You throw a rock straight up from the edge of a cliff. It leaves your hand at time t = 0 moving at 13.0 m/s. Air resistance can be neglected. Find both times at which the rock is 4.00 m above where it left your hand. Enter your answers in ascending order separated by a comma. Express your answer in seconds.

Answers

Answer 1

Answer:

0.36s, 2.3s

Explanation:

Let gravitational acceleration g = 9.81 m/s2. And let the throwing point as the ground 0 for the upward motion. The equation of motion for the rock leaving your hand can be written as the following:

[tex]s = v_0t + gt^2/2[/tex]

where s = 4 m is the position at 4m above your hand. [tex]v_0 = 13 m/s[/tex] is the initial speed of the rock when it leaves your hand. g = -9.81m/s2 is the deceleration because it's in the downward direction. And t it the time(s) it take to get to 4m, which we are looking for

[tex]4 = 13t - 9.81t^2/2[/tex]

[tex]4.905 t^2 - 13t + 4 = 0[/tex]

[tex]t= \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}[/tex]

[tex]t= \frac{13\pm \sqrt{(-13)^2 - 4*(4.905)*(4)}}{2*(4.905)}[/tex]

[tex]t= \frac{13\pm9.51}{9.81}[/tex]

t = 2.3 or t = 0.36

Answer 2

Explanation:

Below is an attachment containing the solution.

You Throw A Rock Straight Up From The Edge Of A Cliff. It Leaves Your Hand At Time T = 0 Moving At 13.0

Related Questions

Two insulated wires, each 4.42 m long, are taped together to form a two-wire unit that is 4.42 m long. One wire carries a current of 7.33 A; the other carries a smaller current I in the opposite direction. The two-wire unit is placed at an angle of 69.4o relative to a magnetic field whose magnitude is 0.547 T. The magnitude of the net magnetic force experienced by the two-wire unit is 2.24 N. What is the current I

Answers

Answer:

Current I=6.34A

Explanation:

Given data

L=L₁=L₂=4.42 m

I₁=7.33A

Angle α=69.4°

B=0.547T

Force F=2.24N

Required

Current I

Solution

The length of each wire ,the magnetic field B,and the angle are same for both wires.

As we know that Force is:

[tex]F_{net}=I_{1}LBSin\alpha -I_{2}LBSin\alpha\\F_{net}=(I_{1}-I_{2})LBSin\alpha\\I_{2}=I_{1}-\frac{F_{net}}{LBSin\alpha}\\I_{2}=7.33A-\frac{2.24N}{(4.42m)(0.547T)Sin(69.4)} \\I_{2}=6.34A[/tex]    

Current I=6.34A

Two large metal plates are separated by 2.67 cm. One plate has a negative charge, and the other plate has a positive charge. The negative plate is heated until an electron barely comes loose from its surface. The electron then accelerates between the plates and strikes the positive plate moving at a speed of 1.32x107 m/s. What is the voltage between the plates

Answers

Answer:

voltage between the plates is 4.952 × [tex]10^{-26}[/tex] V

Explanation:

given data

plate separated distance = 2.67 cm

electron speed = 1.32 × [tex]10^{7}[/tex]  m/s

solution

we will get here first force that is express as

force in parallel plate F = [tex]\frac{eV}{d}[/tex]   ..............1

and force by Newton second law F = ma   .............2

equate equation 1 and 2

ma = [tex]\frac{eV}{d}[/tex]    .................3

and here we know as kinematic equation

v²- u² = 2 × a × s    ...........4

so for initial speed acceleration will be

a = [tex]\frac{v^2-u^2}{2\times s}[/tex]  

a = [tex]\frac{(1.32 \times 10^7)^2}{2\times 2.67 \times 10^{-2}}[/tex]  

a = 3.262 × [tex]10^{-13}[/tex]  m/s²

now we put a in equation 3 and we get v

ma = [tex]\frac{eV}{d}[/tex]

9.1093 × [tex]10^{-31}[/tex] × 3.262 × [tex]10^{-13}[/tex]  = [tex]\frac{1.602 \times 10^{-19} V}{2.67 \times 10^{-2}}[/tex]  

solve it we get

v = 4.952 × [tex]10^{-26}[/tex] V

A block with mass 0.50 kg is forced against a horizontal spring of negligible mass, compressing the spring a distance of 0.20 m (Fig. P7.39). When released, the block moves on a horizontal tabletop for 1.00 m before coming to rest. The force constant k is 100 N>m. What is the coefficient of kinetic friction mk between the block and the tabletop?

Answers

Answer:

μk = 0.408

Explanation:

Given:

m=0.50 Kg,

Let compressed distance x = 0.20 m, and

stretched distance after releasing y = 1.00 m

K = 100 N/M

Sol:

Law of conservation of energy

Energy dissipation due to friction = P.E stores in the spring

Ff * y = 1/2 K x ²   (Ff = μk Fn)  And (Fn = mg) so

μk mgy  =   1/2 K x ²

μk = 1/2 K x ² /mgy   Putting values

μk = (1/2 ) (100 N/M) (0.20 m)² / (0.50 Kg x 9.8 m/s² x 1 m)

μk = 0.408

Answer:

0.4

Explanation:

(i) Since the mass is forced against the spring, an elastic energy ([tex]E_{E}[/tex]) due to the compression of the spring by the force is produced and is given according to Hooke's law by;

[tex]E_{E}[/tex] = [tex]\frac{1}{2}[/tex] k c²            --------------------------------(i)

Where;

k = spring's constant

c = compression caused on the spring.

From the question;

k = 100N/m

c = 0.20m

Substitute these values into equation (i) as follows;

[tex]E_{E}[/tex] = [tex]\frac{1}{2}[/tex] x 100 x 0.20²

[tex]E_{E}[/tex] = 2J

(ii) Now, when the mass is released, it causes the block to move some distance until it stops thereby doing some work within that distance. This means that the elastic energy is converted to workdone. i.e

[tex]E_{E}[/tex] = W          ------------(ii)

The work done (W) is given by the product of the net force(F) on the block and the distance covered(s). i.e

W = F x s           -----------------(iii)

But, the only force acting on the body as it moves is the frictional force ([tex]F_{R}[/tex]) acting to oppose its motion. i.e

F = [tex]F_{R}[/tex]

Where;

[tex]F_{R}[/tex] = μN      [μ = coefficient of kinetic friction, N = mg = normal reaction between the block and the tabletop, m = mass of the block, g = gravity]

[tex]F_{R}[/tex] = μ x mg

Substitute F = [tex]F_{R}[/tex] = μ x mg into equation (iii) as follows;

W = μ x mg x s             ----------------(iv)

Now substitute the value of W into equation (ii) as follows;

[tex]E_{E}[/tex] = μ x mg x s                ------------------(v)

Where;

[tex]E_{E}[/tex] = 2 J               [as calculated above]

m = 0.50 kg

s = distance moved by block = 1.00m

g = 10m/s²            [a known constant]

Substitute these values into equation (v) as follows;

2 = μ x 0.50 x 10 x 1

2 = 5μ

μ = 2 / 5

μ = 0.4

Therefore, the coefficient of kinetic friction between the block and the tabletop is 0.4

A rigid body rotates about a fixed axis with a constant angular acceleration. Which one of the following statements is true concerning the tangential acceleration of any point on the body?

a. The tangential acceleration is zero m/s^2.
b. The tangential acceleration depends on the change in the angular velocity.
c. The tangential acceleration is constant in both magnitude and direction.
d. The tangential acceleration depends on the angular velocity.
e. The tangential acceleration is equal to the centripetal

Answers

Final answer:

The tangential acceleration of a point on a rotating rigid body with constant angular acceleration depends on the change in the angular velocity. It's represented by the formula a_t = r * α, thus can change if the radius changes, even if the angular acceleration is constant.

Explanation:

In this case, a rigid body rotates about a fixed axis with constant angular acceleration. The tangential acceleration of any point on the body would depend on the change in the angular velocity, making the correct answer (b). This is because the tangential acceleration is directly proportional to the angular acceleration and the distance from the axis of rotation, as represented by the formula a_t = r * α, where a_t is the tangential acceleration, r is the radius, and α is the angular acceleration.

Therefore, if the angular acceleration is constant, the tangential acceleration can change if the radius changes. However, if the radius is also constant, then the tangential acceleration will be constant in magnitude, but its direction will change as the direction of the tangent to the motion changes.

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Final answer:

The tangential acceleration of a point on a rotating body with constant angular acceleration depends on the change in the angular velocity. This is due to the relationship defined by the equation for tangential acceleration at = α x r.

Explanation:

In the context of a rigid body rotating about a fixed axis with constant angular acceleration, the correct statement in relation to the tangential acceleration of any point on the body would be: b. The tangential acceleration depends on the change in the angular velocity.

This is because, in physics, tangential acceleration is a measure of how the tangential velocity of a point at a certain radius changes with time. It is directly proportional to the angular acceleration (α) and the radius (r), expressed by the equation at = α x r. Therefore, the tangential acceleration will change as the angular velocity changes, provided there is angular acceleration.

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A large block is being pushed against a smaller block such that the smaller block remains elevated while being pushed. The mass of the smaller block is m = 0.45 kg. It is found through repeated experimentation that the blocks need to have a minimum acceleration of a = 13 m / s 2 in order for the smaller block to remain elevated and not slide down. What is the coefficient of static friction between the two blocks?

Answers

Explanation:

According to the free body diagram a block of mass m will have expression for force as follows.

                  N = ma

and,       [tex]f_{c} - mg[/tex] = 0  

             [tex]\mu_{s}N - mg[/tex] = 0

       [tex]\mu_{s} = \frac{mg}{N}[/tex] = [tex]\frac{mg}{ma}[/tex]

                  = [tex]\frac{g}{a}[/tex]

                  = [tex]\frac{9.8}{13}[/tex]

                  = 0.75

Therefore, we can conclude that the value of coefficient of static friction between the two blocks is 0.75.

The coefficient of static friction between the large block and smaller block is equal to 0.754.

Given the following data:

Mass of smaller block (m) = 0.45 kg.Acceleration (a) = [tex]13 \;m/s^2[/tex]

Acceleration due to gravity = 9.8 [tex]m/s^2[/tex]

To determine the coefficient of static friction between the large block and smaller block:

A force of static friction can be defined as the frictional force that resists the relative motion of two (2) surfaces.

Hence, a force of static friction is a frictional force that keeps an object at rest or stationary rather than being in relative motion.

Mathematically, the force of static friction is given by the formula;

[tex]Fs = uFn[/tex]

Where;

Fs represents the force of static friction.μ represents the coefficient of friction.Fn represents the normal force.

For these block systems, the forces acting on them is given by:

[tex]uma - mg = 0\\\\uma = mg\\\\ua =g\\\\u=\frac{g}{a}[/tex]

Substituting the parameters into the formula, we have;

[tex]u=\frac{9.8}{13}[/tex]

u = 0.754

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A 15-turn rectangular loop of wire of width 10 cm and length 20 cm has a current of 2.5 A flowing through it. Two sides of the loop are oriented parallel to a uniform magnetic field of strength 0.037 T, and the other two sides are perpendicular to the magnetic field. A)What is the magnitude of the magnetic moment of the loop?B)What torque does the magnetic field exert on the loop?

Answers

Answer:

(a) the magnitude of the magnetic moment of the loop is  0.75 Am²

(b) the torque the magnetic field exerts on the loop is 0.028 N.m

Explanation:

Given;

number of turns, N = 15

width of the loop, w = 10 cm = 0.1 m

length of loop, L = 20 cm = 0.2 m

current through the loop, I  = 2.5 A

strength of the magnetic field, B = 0.037 T

Area of the loop, A = L x w = 0.2 x 0.1 = 0.02 m²

Part (a) the magnitude of the magnetic moment of the loop

μ = NIA

where;

μ is the magnitude of the magnetic moment of the loop

μ = 15 x 2.5 x 0.02 = 0.75 Am²

Part (b) the torque the magnetic field exerted on the loop

τ = μB

where;

τ is the torque the magnetic field exerts on the loop

τ = μB = 0.75 x 0.037 = 0.028 N.m

Given Information:

Magnetic field = B =  0.037 T

Current = I = 2.5 A

Number of turns = N = 15 turns

Length of rectangular coil = L = 20 cm = 0.20 m

Width of rectangular coil = W = 10 cm = 0.10 m

Required Information:

(a) Magnetic moment = µ = ?

(b) Torque = τ = ?

Answer:

(a) Magnetic moment = 0.75 A.m ²

(b) Torque = 0.0277 N.m

Explanation:

(a) The magnetic moment µ is given by

µ = NIA

Where µ is the magnetic, N is the number of turns, I is the current, A is the area of rectangular loop and is given by

A = W*L

A = 0.10*0.20

A = 0.02 m²  

µ = 15*2.5*0.02

µ = 0.75 A.m²

(b) The toque τ exerted on current carrying loop with A area in the presence of a magnetic field B is given by

τ = NIAB

τ = 15*2.5*0.02*0.037

τ = 0.0277 N.m

Alternatively,

τ = µB

τ = 0.75*0.037

τ = 0.0277 N.m

A transformer is to be used to provide power for a computer disk drive that needs 6.4 V (rms) instead of the 120 V (rms) from the wall outlet. The number of turns in the primary is 405, and it delivers 500 mA (the secondary current) at an output voltage of 6.4 V (rms). Find the current in the primary.

Answers

Answer:

The current in the primary is 0.026 A

Explanation:

Using the formula

I1 = (V1/V2)*I2

we have

I1 = (6.4/120)*0.500

I1 = 0.026 A

To find the current in the primary coil of a transformer, we use the power equivalence between the primary and secondary sides, and solve for the primary current using the given voltages and secondary current. This results in a primary current of 26.7 mA.

Calculating the Primary Current in a Transformer

To determine the primary current in a transformer, we need to use the relationship between the power in the primary and secondary circuits. The power delivered by an ideal transformer is the same on both sides, which means Powerprimary = Powersecondary. This can be written as:

Vprimary × Iprimary = Vsecondary × Isecondary

Given parameters are:

Vprimary = 120 V (rms)Vsecondary = 6.4 V (rms)Isecondary = 500 mA = 0.5 A

We first calculate the power on the secondary side:

Powersecondary = Vsecondary × Isecondary = 6.4 V × 0.5 A = 3.2 W

For an ideal transformer, this power must be equal to the power on the primary side:

[tex]Powerprimary = Vprimar *Iprimary[/tex]

Thus, we have:

3.2 W = 120 V × [tex]Iprimary[/tex]

Solving for [tex]Iprimary[/tex], we get:

[tex]Iprimary[/tex] = 3.2 W / 120 V = 0.0267 A = 26.7 mA

Therefore, the current in the primary coil is 26.7 mA.

A hot water stream at 80 oC enters a mixing chamber with mass flow rate of 3.6 kg/s and mixed with cold water at 20 oC. If the mixture temperature is 42 oC, determine the mass flow rate of cold stream in kg/min. Assume all the streams being at 250 kPa

Answers

Explanation:

The mixing chamber will be well insulated when steady operating conditions exist such that there will be negligible heat loss to the surroundings. Therefore, changes in the kinetic and potential energies of the fluid streams will be negligible and there are constant fluid properties with no work interactions.

   [tex]T < T_{sat}[/tex] at 250 kPa = [tex]127.41^{o}C[/tex]

   [tex]h_{1}[/tex] approx equal to [tex]h_{f}[/tex] at [tex]80^{o}C[/tex]

              = 335.02 kJ/kg

    [tex]h_{2}[/tex] ≈ [tex]h_{f}[/tex] at [tex]20^{o}C[/tex]

                      = 83.915 kJ/kg

and,    [tex]h_{3}[/tex] ≈ [tex]h_{f}[/tex] at [tex]42^{o}C[/tex] = 175.90 kJ/kg

Therefore, mass balance will be calculated as follows.

   [tex]m^{o}_{in} - m^{o}_{out} = \Delta m^{o}_{system} \rightarrow m^{o}_{1} + m^{o}_{2} = m^{o}_{3}[/tex]

And, energy balance will be given as follows.

      [tex]E^{o}_{in} - E^{o}_{out} = \Delta E^{o}_{system}[/tex]

As we are stating steady conditions,

     [tex]\Delta m^{o}_{system}[/tex] and [tex]\Delta E^{o}_{system}[/tex] cancel out to zero.

So,    [tex]E^{o}_{in} = E^{o}_{out}[/tex]

     [tex]m^{o}_{1}(h_{1}) + m^{o}_{2}(h_{2}) = m^{o}_{3}(h_{3})[/tex]

On combining the relations, we solve for [tex]m^{o}_{2}[/tex] as follows.

   [tex]m^{o}_{1}(h_{1}) + m^{o}_{2}(h_{2}) = (m^{o}_{1} + m^{o}_{2})(h_{3})[/tex]

   [tex]m^{o}_{2} = (\frac{(h_{1} - h_{3})}{(h_{3} - h_{2})}) \times m^{o}_{1}[/tex]

              = [tex]\frac{(335.02 - 175.90)}{(175.90 - 83.915)} \times 0.5[/tex]  

       [tex]m^{o}_{2}[/tex] = 0.865 kg/s

                       = 51.9 kg/min      (as 1 min = 60 sec)

Thus, we can conclude that the mass flow rate of cold stream is 51.9 kg/min.

A truck moving at 35.0mph collides head on with a car traveling in the opposite direction. The mass of the car is 550 kg, the mass of the truck is 2200 kg. During thecollision both vehicles come to a stop in 0.150s as the front end of both vehicles’crumples. What was the acceleration of the car? Assume that during the collision the acceleration of each vehicle is constant.Also, assume that frictional force are small compared to the forces compared to the contact forces between the vehicles during the colision.

Answers

Answer:

Explanation:

Check attachment for solution

A horizontal uniform plank is supported by ropes I and II at points P and Q, respectively, as shown above. The two ropes have negligible mass. The tension in rope I is 150 N. The point at which rope II is attached to the plank is now moved to point R halfway between point Q and point C, the center of the plank. The plank remains horizontal. What are the new tensions in the two ropes?

The answer is T1=100N and T2=200N but I don't know the steps to solve this one. An explanation would be much appreciated.

Answers

Explanation:

There are three forces on the plank.  T₁ pulling up at point P, T₂ pulling up at point Q, and W pulling down at point C.

Let's say the length of the plank is L.

Sum of forces in the y direction before rope II is moved:

∑F = ma

150 N + 150 N − W = 0

W = 300 N

Sum of moments about point P after rope II is moved:

∑τ = Iα

(T₁) (0) − (300 N) (L/2) + (T₂) (3L/4) = 0

-(300 N) (L/2) + (T₂) (3L/4) = 0

-(300 N) (1/2) + (T₂) (3/4) = 0

-150 N + 3/4 T₂ = 0

T₂ = 200 N

Sum of forces in the y direction:

∑F = ma

T₁ + 200 N − 300 N = 0

T₁ = 100 N

The new tensions in the two ropes after the movement of rope 2 are;

T₁ = 100 N

T₁ = 100 NT₂ = 200 N

We are told that as the plank is currently, the two ropes attached at each end have tension of 150 N each.

Thus;

T₁ = T₂ = 150 N

The two ropes are acting in tension upwards and so for the plank to be balanced, there has to be a downward force(which is the weight of the plank) must be equal to the sum of the tension in the two ropes.

Thus, from equilibrium of forces, we have;

W = T₁ + T₂

W = 150 + 150

W = 300 N

Now, we are told that;

Rope 2 is now moved to a point R which is halfway between point C and Q. Since C is the centre of the plank and R is the midpoint of C and Q, if the length of the plank is L, then the distance of rope 2 from point P is now ¾L.

Since the plank remains horizontal after shifting the rope 2 to point R, let us take moments about point P to get;

T₂(¾L) - W(½L) = 0

Plugging in the relevant values;

T₂(¾L) - 300(½L) = 0

T₂(¾L) - 150L = 0

Rearrange to get;

T₂(¾L) = 150L

Divide both sides by L to get;

T₂(¾) = 150

Cross multiply to get;

T₂ = 150 × 4/3

T₂ = 200 N

Thus;

T₁ = 300 - 200

T₁ = 100 N

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X rays of 25 keV are received with an X - ray intensifying screen that produces light photons at 425 nm. If the conversion effi ciency of intensifying screen is 20%, calculate how many light photons will be generated by an X - ray photon.

Answers

Answer:

Photons Generated= ~1715 photons

Explanation:

The detailed explanation of answer is given in attached file.

A rod of m= 1.3 kg rests on two parallel rails that are L = 0.42 m apart. The rod carries a current going between the rails (bottom to top in the figure) with a magnitude 1 = 2.6 A. A uniform magnetic field of magnitude B = 0.35 T pointing upward is applied to the region, as shown in the graph. The rod moves a distance d=1.25 m. Ignore the friction on the rails. † † † Ē I Otheexpertta.com A Calculate the final speed, in meters per second, of the rod if it started from rest, assuming there is no friction in the contact between it and rails.Calculate the final speed, in meters per second, of the rod if it started from rest, assuming there is no friction in the contact between it and rails. Assume the current through the rod is constant at all times.

Answers

Answer:

The final speed of the rod is 0.86 m/s.

Explanation:

Given that,

Mass of rod = 1.3 kg

Distance between rail= 0.42 m

Current = 2.6 A

Magnetic field = 0.35 T

Distance = 1.25 m

We need to calculate the acceleration

Using formula of magnetic force

[tex]F= Bil[/tex]

[tex]ma=Bil[/tex]

[tex]a=\dfrac{Bil}{m}[/tex]

Put the value into the formula

[tex]a=\dfrac{0.35\times2.6\times0.42}{1.3}[/tex]

[tex]a=0.294\ m/s^2[/tex]

We need to calculate the final speed of the rod

Using equation of motion

[tex]v^2-u^2=2as[/tex]

Put the value in the equation

[tex]v^2=2\times0.294\times1.25[/tex]

[tex]v=0.86\ m/s[/tex]

Hence, The final speed of the rod is 0.86 m/s.

The final speed of the rod is 0.86 m/s.

What is Speed?

This refers to the rate of change of the position of an object in a specified direction.

The ParameterMass of rod = 1.3 kgDistance between rail= 0.42 mCurrent = 2.6 AMagnetic field = 0.35 TDistance = 1.25 m

To calculate the acceleration

We use the formula of magnetic force

a=Bil/m

a= (0.35 x 2.6 x 0.42)/1.3

a= 0.294m/s^2

Then the final speed of the rod

We use the equation of motion

v^2 - u^2= 2as

=> v^2= 0.86m/s

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In a cloud chamber experiment, a proton enters a uniform 0.280 T magnetic field directed perpendicular to its motion. You measure the proton's path on a photograph and find that it follows a circular arc of radius 6.12 cm. How fast was the proton moving?

Answers

Answer:

The proton was moving at a speed of 1.64 x 10⁶ m/s

Explanation:

Given;

strength of magnetic field, B = 0.280 T

circular radius, R = 6.12 cm

mass of proton, m = 1.67 x 10⁻²⁷ kg

charge of electron. q = 1.602 x 10⁻¹⁹ C

When the proton follows a circular arc, then magnetic force will be equal to the centripetal force.

Magnetic force, Fm = qvB

Centripetal force, Fr = mv²/R

Fm = Fr

qvB = mv²/R

[tex]qvB = \frac{Mv^2}{R} \\\\\frac{qBR}{M} = \frac{v^2}{v} \\\\v =\frac{qBR}{M} = \frac{1.602*10^{-19} *0.28*0.0612}{1.67*10^{-27}} =1.64 *10^6 \ m/s[/tex]

Therefore, the proton was moving at a speed of 1.64 x 10⁶ m/s

Given Information:

Magnetic field = B = 0.280 T

Radius = r = 6.12 cm = 0.0612 m

Required Information:  

Speed of proton = v = ?

Answer:

Speed of proton = v = 1641.77x10³ m/s

Explanation:

Since the proton is moving in a circular path we can model it in terms of magnetic force and centripetal force.

The magnetic force is given by

F = qvB

The centripetal force is given by

F = mv²/r

equating the both equations yields,

mv²/r = qvB

mv = qBr

v = qBr/m

Where q = 1.6x10⁻¹⁹ C is the of the proton, m = 1.67x10⁻²⁷ kg is the mass of proton, B is the magnetic field and r is the radius o circular arc around which proton is moving.

v = 1.6x10⁻¹⁹*0.280*0.0612/1.67x10⁻²⁷

v = 1641772.45 m/s

v = 1641.77x10³ m/s

Therefore, the proton is moving at the speed of 1641.77x10³ m/s.

A piston–cylinder device initially contains 2 L of air at 100 kPa and 25°C. Air is now compressed to a final state of 600 kPa and 150°C. The useful work input is 1.2 kJ. Assuming the surroundings are at 100 kPa and 25°C, determine (a) the exergy of the air at the initial and the final states, (b) the minimum work that must be supplied to accomplish this compression process, and (c) the second-law efficiency of this process.

Answers

Answer:

a. The energy of the air at the initial and the final states is 0kJ and 0.171kJ respectively

b. 0.171kJ

c. 0.143

Explanation:

a.

Because there are same conditions of the state of air at the surroundings and at the Initial stage, the energy of air at the Initial stage is 0kJ.

Calculating energy at the final state;

We start by calculating the specific volume of air in the environment and at the final state.

U2 = At the final state, it is given by

RT2/P2

U1= At the Initial state, it is given by

RT1/P1

Where R = The gas constant of air is 0.287 kPa.m3/kg

T2 = 150 + 273 = 423K

T1 = 25 + 273 = 298K

P2 = 600KPa

P1 = 100KPa

U2 = 0.287 * 423/600

U2 = 0.202335m³/kg

U1 = 0.287 * 298/100

U1 = 0.85526m³/kg

Then we Calculate the mass of air using ideal gas relation

PV = mRT

m = P1V/RT1 where V = 2*10^-3kg

m = 100 * 2 * 10^-3/(0.287 * 298)

m = 0.00234kg

Then we calculate the entropy difference, ∆s. Which is given by

cp2 * ln(T2/T1) - R * ln(P2/P1)

Where cp2 = cycle constant pressure = 1.005

∆s = 1.005 * ln (423/298) - 0.287 * ln(600/100)

∆s = -0.1622kJ/kg

Energy at the final state =

m(E2 - E1 + Po(U2 - U1) -T0 * ∆s)

E2 and E1 are gotten from energy table as 302.88 and 212.64 respectively

Energy at the final state

= 0.00234(302.88 - 212.64 + 100(0.202335 - 0.85526) - 298 * -0.1622)

Energy at the final state = 0.171kJ

b.

Minimum Work = ∆Energy

Minimum Work = Energy at the final state - Energy at the initial state

Minimum Work = 0.171 - 0

Minimum Work done = 0.171kJ

c. The second-law efficiency of this process is calculated by ratio of meaningful and useful work

= 0.171/1.2

= 0.143

Final answer:

Exergy measures the maximum work a system can produce. To calculate its change and consequently the minimum work supplied and second-law efficiency, additional data like specific heats are required.

Explanation:

This involves thermodynamics, a branch of physics that deals with energy transfer. Specifically, this question is about the concept of exergy, a measure of the maximum amount of work a system can produce with respect to its environment.

(a) The exergy (or available energy) of a system in a given state is the maximum theoretical work that can be obtained as the system communicates with an equilibrium state. In this case, the initial and final states of the system are given, but we need more data such as the specific heats, to compute the initial and final exergies.

(b) The minimum work that must be supplied is equivalent to the change in exergy from the initial to the final state, but again, it cannot be determined without knowing the specific heat values of air

(c) The second-law efficiency is defined as the ratio of the actual work to the work done in a reversible process. Here, it is the ratio of the useful work input (1.2 kJ) to the minimum work needed for the compression process. To find the exact efficiency, we need to compute the minimum required work, which would require the specific heat values.

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2 m3 of an ideal gas are compressed from 100 kPa to 200 kPa. As a result of the process, the internal energy of the gas increases by 10 kJ, and 150 kJ of heat is transferred to the surroundings. How much work was done by the gas during the process?

Answers

Answer:

work done is -150 kJ

Explanation:

given data

volume v1 = 2 m³

pressure p1 = 100 kPa

pressure p2 = 200 kPa

internal energy = 10 kJ

heat is transferred  = 150 kJ

solution

we know from 1st law of thermodynamic is

Q = du +W    ............1

put here value and we get

-140 = 10 + W

W = -150 kJ

as here work done is -ve so we can say work is being done on system

Final answer:

The work done by the gas during the compression where 2 m³ of an ideal gas is compressed from 100 kPa to 200 kPa, with an internal energy increase of 10 kJ, and 150 kJ of heat transferred to the surroundings, is -160 kJ.

Explanation:

The student has asked how much work was done by the gas during a compression process in which 2 m³ of an ideal gas is compressed from 100 kPa to 200 kPa, the internal energy increases by 10 kJ, and 150 kJ of heat is transferred to the surroundings. To find the work done by the gas, we can use the first law of thermodynamics, which states that the change in internal energy (ΔU) is equal to the heat added to the system (Q) minus the work done by the system (W). The formula is ΔU = Q - W.

In this scenario, we have ΔU as +10 kJ (because the internal energy increases) and Q as -150 kJ (because heat is transferred to the surroundings, meaning it is leaving the system, thus it's a negative value). Plugging these values into the first law of thermodynamics gives us:

10 kJ = -150 kJ - W

When we rearrange the equation to solve for W, it becomes:

W = -150 kJ - 10 kJ

W = -160 kJ

Since work done by the system is a negative value in this case, it indicates that 160 kJ of work has been done on the gas by the surroundings during the compression. Thus, the work done by the gas itself is -160 kJ.

An initially uncharged 4.07 μF capacitor and a 7.71 k Ω resistor are connected in series to a 1.50 V battery that has negligible internal resistance. What is the initial current in the circuit, expressed in milliamperes?

Answers

Answer:

I₀ = 0.2 mA

Explanation:

Just after being connected, as the voltage between plates of a capacitor can't change instantanously, the initial voltage through the capacitor must be zero, so it presents like a short to the battery.So, in these circumstances, as the battery only "sees"a resistor, the initial current can be found applying Ohm's law to the resistor, as follows:

        [tex]V = I_{0}*R \\\\ I_{0} = \frac{V}{R} = \frac{1.50V}{7.71e3\Omega} = 0.2 mA[/tex]

The initial current (that will be diminishing as the capacitor charges), is 0.2 mA.
Answer:

0.19mA

Explanation:

Given;

Capacitor of capacitance = 4.07 μF

Resistor of resistance = 7.71 kΩ = 7.71 x 1000Ω  = 7710Ω

Voltage = 1.50V

Since the capacitor is initially uncharged, it behaves like a short circuit. Therefore, the only element drawing current at that instant is the resistor.  This means that the initial current in the circuit is the one due to (flowing through) the resistor.

And since there is negligible internal resistance, the emf of the battery is equal to the voltage supplied by the battery and is used to supply current to the resistor. Therefore, according to Ohm's law;

V = I x R           ---------------(i)

Where;

V = voltage supplied or the emf

I = current through the resistor

R = resistance of the resistor

Substitute the values of V and R into equation (i) as follows;

1.50 = I x 7710

I = [tex]\frac{1.5}{7710}[/tex]

I = 0.00019A

Multiply the result by 1000 to convert it to milliamperes as follows;

0.00019 x 1000 mA = 0.19mA

Therefore, the initial current in the circuit, expressed in milliamperes is 0.19

A battery with an emf of 4 V and an internal resistance of 0.7 capital omega is connected to a variable resistance R. Find the current and power delivered by the battery when R is (a) 0, I = 5.714285714 A * [1.25 points] 1 attempt(s) made (maximum allowed for credit = 5) [after that, multiply credit by 0.5 up to 10 attempts] 5.714285714 OK P = 0 W * [1.25 points] 3 attempt(s) made (maximum allowed for credit = 5) [after that, multiply credit by 0.5 up to 10 attempts] 0 OK (b) 5 capital omega, I = 0.701754386 A * [1.25 points] 1 attempt(s) made (maximum allowed for credit = 5) [after that, multiply credit by 0.5 up to 10 attempts] 0.701754386 OK P = 2.462296091 W * [1.25 points] 1 attempt(s) made (maximum allowed for credit = 5) [after that, multiply credit by 0.5 up to 10 attempts] 2.462296091 OK (c) 10 capital omega, and I = 0.3738317757 A * [1.25 points] 1 attempt(s) made (maximum allowed for credit = 5) [after that, multiply credit by 0.5 up to 10 attempts] 0.3738317757 OK P = 1.397501965 W * [1.25 points] 1 attempt(s) made (maximum allowed for credit = 5) [after that, multiply credit by 0.5 up to 10 attempts] 1.397501965 OK (d) infinite. I = 0 A * [1.25 points] 1 attempt(s) made (maximum allowed for credit = 5) [after that, multiply credit by 0.5 up to 10 attempts] 0 OK P = W

Answers

Answer:

E = I(R + r)

Making I the subject of the formular by dividing both sides by R + r,

I = E/(R + r)

E = 4V, r = 0.7Ohm, R = 0

I = 4/(0 + 0.7) = 4/0.7

I = 5.174285714A

Explanation:

For a cell of emf E, internal resistance r, connected to an external resistance R, the current flowing through the circuit will be given as:

I = E/(R + r). I is measured in Amperes(A), emf in volts(V), R in Ohms and internal resistance r also in ohms

You need to push a heavy box across a rough floor, and you want to minimize the average force applied to the box during the time the box is being pushed. Which method of pushing results in the minimum average force being applied to the box?

A. Keep pushing the box forward at a steady speed.
B. Push the box forward a short distance, rest, then repeat until finished,
C. Push the box so that it accelerates forward at a constant rate.

Answers

Answer:A. Keep pushing the box forward at a steady speed.

Explanation: Frictional force is a resistant force which oppose the Movement of an object, frictional force can emanate from a rough surface.

When an object that is moving with a consistent force is opposed by the roughness of the surface through which it is moving,it will cause the object to continue to move with a reduced speed as it goes along.

WHEN YOU APPLY A CONSTANT FORCE ON A MOVING OBJECT THAT IS OPPOSED BY A ROUGH SURFACE IT WILL RESULT IN AN AVERAGE MINIMAL FORCE BEING APPLIED TO THE OBJECT.

A 4.0 cm × 4.2 cm rectangle lies in the xy-plane. You may want to review (Pages 664 - 668) . Part A What is the electric flux through the rectangle if E⃗ =(150ı^−200k^)N/C? Φe = N⋅m2/C Previous AnswersRequest Answer Incorrect; Try Again; 5 attempts remaining Part BPart complete What is the electric flux through the rectangle if E⃗ =(150ı^−200ȷ^)N/C? Φe = 0 N⋅m2/C

Answers

Answer:

Explanation:

Area, A = 4 cm x 4.2 cm = 16.8 cm²

A).

[tex]\overrightarrow{E}=150\widehat{i}-200\widehat{k}[/tex]

Area is in x y plane so

[tex]\overrightarrow{A}=16.8\times 10^{-4}\widehat{k}[/tex]

Electric flux,

[tex]\phi =\overrightarrow{E}.\overrightarrow{A}[/tex]

[tex]\phi =\left ( 150\widehat{i}-200\widehat{k} \right ).\left (16.8\times 10^{-4}\widehat{k} \right )[/tex]

Ф = 0.336 Nm²/C

B).

[tex]\overrightarrow{E}=150\widehat{i}-200\widehat{j}[/tex]

[tex]\phi =\overrightarrow{E}.\overrightarrow{A}[/tex]

[tex]\phi =\left ( 150\widehat{i}-200\widehat{j} \right ).\left (16.8\times 10^{-4}\widehat{k} \right )[/tex]

Ф = 0 Nm²/C

The maximum electric field 9.8 m from a point light source is 3.0 V/m. What are (a) the maximum value of the magnetic field and (b) the average intensity of the light there? (c) What is the power of the source?

Answers

Answer:

maximum value of the magnetic field  B  = 1 ×[tex]10^{-8}[/tex] T

average intensity of the light = 0.011937 W/m²

power of source =  14.40 J

Explanation:

given data

maximum electric field E = 3.0 V/m

distance from a point source r = 9.8 m

solution

first we get here maximum value of the magnetic field  

maximum value of the magnetic field   = [tex]\frac{E}{C}[/tex]   .........1

maximum value of the magnetic field   = [tex]\frac{3}{3 \times 10^8}[/tex]

maximum value of the magnetic field  B  = 1 ×[tex]10^{-8}[/tex] T

and

now we get average intensity of the light that is

average intensity of the light =  [tex]\frac{EB}{2\mu _o}[/tex]   .........2

average intensity of the light = [tex]\frac{3 \times 1 \times 10^{-8}}{2 \times 4\pi \times 10^{-7}}[/tex]  

average intensity of the light = 0.011937 W/m²

and

now we get power of source that is express as

power of source = average intensity × 4×π×r²   ..........3

power of source = 0.011937 × 4×π×9.8²

power of source =  14.40 J

A skater extends her arms, holding a 2 kg mass in each hand. She is rotating about a vertical axis at a given rate. She brings her arms inward toward her body in such a way that the distance of each mass from the axis changes from 1.00 to 0.50 m. Her rate of rotation (neglecting the mass of the skater) will the final angular velocity (in rev/s) be if her moment of inertia remains approximately constant at 5kg(m2), and the distance of the masses from the axis changes from 1 m to 0.1m?a. 6b. 3c. 9d. 4e. 7

Answers

Explanation:

It is known that relation between torque and angular acceleration is as follows.

                    [tex]\tau = I \times \alpha[/tex]

and,       I = [tex]\sum mr^{2}[/tex]

So,      [tex]I_{1} = 2 kg \times (1 m)^{2} + 2 kg \times (1 m)^{2}[/tex]

                       = 4 [tex]kg m^{2}[/tex]

      [tex]\tau_{1} = 4 kg m^{2} \times \alpha_{1}[/tex]

     [tex]\tau_{2} = I_{2} \alpha_{2}[/tex]

So,      [tex]I_{2} = 2 kg \times (0.5 m)^{2} + 2 kg \times (0.5 m)^{2}[/tex]

                     = 1 [tex]kg m^{2}[/tex]

 as [tex]\tau_{2} = I_{2} \alpha_{2}[/tex]

                   = [tex]1 kg m^{2} \times \alpha_{2}[/tex]        

Hence,     [tex]\tau_{1} = \tau_{2}[/tex]

                  [tex]4 \alpha_{1} = \alpha_{2}[/tex]

            [tex]\alpha_{1} = \frac{1}{4} \alpha_{2}[/tex]

Thus, we can conclude that the new rotation is [tex]\frac{1}{4}[/tex] times that of the first rotation rate.

Final answer:

The final angular velocity will be approximately 1 rev/s.

Explanation:

First, let's calculate the initial angular velocity using the formula:

Initial Angular Velocity = Initial Moment of Inertia * Initial Angular Velocity / Final Moment of Inertia

Given that the initial moment of inertia is 5 kg(m2), the initial angular velocity is 1 rev/s, and the final moment of inertia is approximately 5 kg(m2), we can calculate the initial angular velocity as follows:  (5 kg(m2) * 1 rev/s / 5 kg(m2)) = 1 rev/s. Therefore, the final angular velocity will also be approximately 1 rev/s.

Suppose that you can throw a projectile at a large enough v0 so that it can hit a target a distance R downrange. Given that you know v0 and R, determine the general expressions for the two distinct launch angles θ1 and θ2 that will allow the projectile to hit D. For v0 = 42 m/s and R = 70 m, determine numerical values for θ1 and θ2?

Answers

Answer:

Theta1 = 12° and theta2 = 168°

The solution procedure can be found in the attachment below.

Explanation:

The Range is the horizontal distance traveled by a projectile. This diatance is given mathematically by Vo cos(theta) t. Where t is the total time of flight of the projectile in air. It is the time taken for the projectile to go from starting point to finish point. This solution assumes the projectile finishes uts motion on the same horizontal level as the starting point and as a result the vertical displacement is zero (no change in height).

In the solution as can be found below, the expression to calculate the range for any launch angle theta was first derived and then the required angles calculated from the equation by substituting the values of the the given quantities.

) A stone initially moving at 8.0 m/s on a level surface comes to rest due to friction after it travels 11 m. What is the coefficient of kinetic friction between the stone and the surface

Answers

Answer:

-0.3

Explanation:

F' = μmg ........... Equation 1

Where F' = Frictional force, μ = coefficient of kinetic friction, m = mass of the stone, g = acceleration due to gravity.

But,

F' = ma ............ Equation 2

Where a = acceleration of the stone.

Substitute equation 2 into equation 1

ma = μmg

dividing both side of the equation by m

a = μg

make μ the subject of the equation

μ = a/g............... Equation 3

From the equation of motion,

v² = u²+2as................. Equation 4

Where v and u are the final and the initial velocity respectively, s = distance.

Given: v = 0 m/s (to rest), u = 8.0 m/s, s = 11 m.

Substitute into equation 4

0² = 8² + 2×11×a

22a = -64

a = -64/22

a = -32/11 m/s² = -2.91 m/s²

substitute the values of a and g into equation 3

μ = -2.91/9.8

μ = -0.297

μ ≈ -0.3

Final answer:

The coefficient of kinetic friction is found using the work-energy principle by equating the initial kinetic energy of the stone to the work done by friction. Given that the stone travels 11 meters and comes to rest, the coefficient of kinetic friction is calculated as approximately 0.296.

Explanation:

To find the coefficient of kinetic friction between the stone and the surface, we need to use the work-energy principle, which states that the work done by all the forces acting on an object is equal to the change in its kinetic energy. Since the stone comes to rest, all of its initial kinetic energy has been converted into work done against friction.

First, let's calculate the initial kinetic energy (KE) of the stone:

KE = (1/2)mv²KE = (1/2)(8.0 m/s)²KE = 32 J (joules)

This energy is equal to the work done by friction (Wf):

Wf = Frictional force (f) x Distance (d)

Since the frictional force is equal to the kinetic friction coefficient (µk) multiplied by the normal force (N), and the normal force is equal to the weight of the stone (mg, where g is the acceleration due to gravity), we can express the work done by friction as:

Wf = µkmgd

Setting the work done by friction equal to the initial kinetic energy gives us:

32 J = µkmg(11 m)

Solving for the coefficient of kinetic friction:

µk = 32 J / (mg x 11 m)

Now, assuming the acceleration due to gravity (g) is 9.8 m/s²:

µk = 32 J / (m x 9.8 m/s² x 11 m)

Since the mass (m) cancels out, we don't need to know it:

µk = 32 J / (9.8 m/s² x 11 m)

µk = 0.296

Therefore, the coefficient of kinetic friction between the stone and the level surface is approximately 0.296.

Nitrogen at an initial state of 300 K, 150 kPa, and 0.2 m3is compressed slowly in an isothermal process to a final pressure of 800 kPa. Determine the work done during this process.

Answers

Answer:

[tex]W=-251096.465\ J[/tex] negativesign denotes thatthe work is consumed by the system.

Explanation:

Given:

Isothermal process.

initial temperature, [tex]T_1=300\ K[/tex]

initial pressure, [tex]P_1=150kPa[/tex]

initial volume, [tex]V_1=0.2\ m^3[/tex]

final pressure, [tex]P_2=800\ kPa[/tex]

The work done during an isothermal process is given by:

[tex]W=P_1.V_1\times ln(\frac{P_1}{P_2} )[/tex]

[tex]W=150\times 1000\times \ln\frac{150}{800}[/tex]

[tex]W=-251096.465\ J[/tex] negativesign denotes thatthe work is consumed by the system.

1 kg ball rolls off a 33 m high cliff, and lands 23 m from the base of the cliff. Express the displacement and the gravitational force in terms of vectors and calculate the work done by the gravitational force. Note that the gravitational force is <0, , 0>, where is a positive number (+9.8 N/kg). (Let the origin be at the base of the cliff, with the direction towards where the ball lands, and the direction taken to be upwards.)

Answers

Answer:

d = <23, 33, 0> m ,    F_W = <0, -9.8, 0> ,   W = -323.4 J

Explanation:

We can solve this exercise using projectile launch ratios, for the x-axis the displacement is

         x = vox t

Y Axis  

         y = [tex]v_{oy}[/tex] t - ½ g t²

It's displacement is

      d = x i ^ + y j ^ + z k ^

Substituting

      d = (23 i ^ + 33 j ^ + 0) m

Using your notation

   d = <23, 33, 0> m

The force of gravity is the weight of the body

         W = m g

        W = 1  9.8 = 9.8 N

In vector notation, in general the upward direction is positive

         W = (0 i ^  - 9.8 j ^ + 0K ^) N

         W = <0, -9.8, 0>

Work is defined

           W = F. dy

             W = F dy cos θ

In this case the force of gravity points downwards and the displacement points upwards, so the angle between the two is 180º

          Cos 180 = -1

           W = -F y

           W = - 9.8 (33-0)

           W = -323.4 J

Under what circumstances are two circuits considered equivalent? A. their input values are the same B. the output of one is the inverse of the output of the other C. their output values are the same for all possible input combinations D. their output values are always 1 E. the input of one matches the output of the other

Answers

Two circuits are considered equivalent when their output values are the same for all possible input combinations.

A circuit equivalent to another is one that meets the same conditions, (eg same current), under a different configuration.

The equivalent circuit made in this way is not the same as the original one, but if the total voltages, the total currents and the total resistance of the circuit will be equal, which will be the equivalent.

The concept of equivalent circuit is used when saying, for example, that a real generator is equivalent to an ideal one with its internal resistance in series.

Therefore, we can conclude that two circuits are considered equivalent when their output values are the same for all possible input combinations.

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Final answer:

Two circuits are considered equivalent if they produce the same output for all possible input combinations, as can be demonstrated using a truth table in digital logic. The correct option is C.

Explanation:

Two circuits are considered equivalent when their output values are the same for all possible input combinations. This means that regardless of the input values, both circuits will produce the same output across all scenarios. For instance, in digital logic, two circuits using different logic gates such as AND, OR, NAND, or XOR would be equivalent if they yield the same output for each combination of inputs, as represented in a truth table. An example of this is the use of De Morgan's laws where an AND gate followed by a NOT gate can be equivalent to a NAND gate, producing the same outputs. Understanding these principles is essential for fields like electronics, computer engineering, and programming. Hence, Option C is correct.

The most soaring vocal melody is in Johann Sebastian Bach's Mass in B minor. In one section, the basses, tenors, altos, and sopranos carry the melody from a low D to a high A. In concert pitch, these notes are now assigned frequencies of 146.8 Hz and 880.0 Hz. (Use 343 m/s as the speed of sound, and 1.20 kg/m3 as the density of air.)

Find the wavelength of the initial note.

Answers

Answer:

2.33651226158 m

Explanation:

From the question the required data is as follows

f = Frequency of the initial note = 146.8 Hz

v = Velocity of sound in air = 343 m/s

The wavelength of a wave is given by

[tex]\lambda=\dfrac{v}{f}[/tex]

[tex]\Rightarrow \lambda=\dfrac{343}{146.8}[/tex]

[tex]\Rightarrow \lambda=2.33651226158\ m[/tex]

The wavelength of the initial note is 2.33651226158 m

A wire of length L is wound into a square coil with 167 turns and used in a generator that operates at 60.0 Hz and 120 V rms value in a 0.041-T magnetic field. What is the length L of the wire used to construct the coil

Answers

Answer:

[tex]171.43m[/tex]

Explanation:

First, define [tex]emf[/tex]( electromotive force )-is the unit electric charge imparted by an energy source. In this case the generator.

The peak emf is:

[tex]E_p_e_a_k=\sqrt2(E_m_a_x)[/tex]=[tex]\sqrt(2\times 120V)=170V[/tex]

Substituting [tex]w=2\pi f[/tex] and the value for peaf [tex]E[/tex] gives:

Total length=[tex]4\sqrt {\frac{NE_p_e_a_k}{Bw}[/tex]=[tex]4\sqrt{\frac{167\times 170}{0.041T\times 2pi \times 60.0Hz}[/tex]

=[tex]171.43m[/tex]

Hence, wire's length is 171.43m

A very long uniform line of charge has charge per unit length 4.54 μC/m and lies along the x-axis. A second long uniform line of charge has charge per unit length -2.58 μC/m and is parallel to the x-axis at y1 = 0.384 m .

What is the magnitude of the net electric field at point y2 = 0.204 m on the y-axis?

Answers

Answer:

The magnitude of the net electric field is [tex]6.57\times10^{5}\ N/C[/tex]

Explanation:

Given that,

Charge density [tex]\lambda = 4.54\ \mu C/m[/tex]

Charge density [tex]\lambda' = -2.58\ \mu C/m[/tex]

Distance [tex]y_{1}= 0.384\ m[/tex]

Distance [tex]y_{2}= 0.204\ m[/tex]

We need to calculate the magnitude of the net electric field

Using formula of electric field

[tex]E=E_{1}+E_{2}[/tex]

[tex]E=\dfrac{1}{2\pi\epsilon_{0}}(\dfrac{\lambda}{r}+\dfrac{\lambda'}{r'})[/tex]

Put the value into the formula

[tex]E=\dfrac{1}{2\pi\times8.85\times10^{-12}}(\dfrac{4.54\times10^{-6}}{0.204}+\dfrac{2.58\times10^{-6}}{0.384-0.204})[/tex]

[tex]E=6.57\times10^{5}\ N/C[/tex]

Hence, The magnitude of the net electric field is [tex]6.57\times10^{5}\ N/C[/tex]

A tradesman sharpens a knife by pushing it with a constant force against the rim of a grindstone. The 30-cm-diameter stone is spinning at 200 rpm and has a mass of 28 kg. The coefficient of kinetic friction between the knife and the stone is 0.2. The stone slows steadily to 180 rpm in 10 s of grinding.

a) What is the magnitude of the angular acceleration of the grindstone as it slows down?

b) With what force does the tradesman press the knife against the grindstone?

Answers

Answer:

a. 0.21 rad/s2

b. 2.205 N

Explanation:

We convert from rpm to rad/s knowing that each revolution has 2π radians and each minute is 60 seconds

200 rpm = 200 * 2π / 60 = 21 rad/s

180 rpm = 180 * 2π / 60 = 18.85 rad/s

r = d/2 = 30cm / 2 = 15 cm = 0.15 m

a)So if the angular speed decreases steadily (at a constant rate) from 21 rad/s to 18.85 rad/s within 10s then the angular acceleration is

[tex]\alpha = \frac{\Delta \omega}{\Delta t} = \frac{21 - 18.85}{10} = 0.21 rad/s^2[/tex]

b) Assume the grind stone is a solid disk, its moment of inertia is

[tex]I = mR^2/2[/tex]

Where m = 28 kg is the disk mass and R = 0.15 m is the radius of the disk.

[tex] I = 28*0.15^2/2 = 0.315 kgm^2[/tex]

So the friction torque is

[tex]T_f = I\alpha = 0.315*0.21 = 0.06615 Nm[/tex]

The friction force is

[tex]F_f = T_f/R = 0.06615 / 0.15 = 0.441 N[/tex]

Since the friction coefficient is 0.2, we can calculate the normal force that is used to press the knife against the stone

[tex]N = F_f/\mu = 0.441/0.2 = 2.205 N[/tex]

Other Questions
In the famous case of H. M., after having part of his brain removed, he could no longer ________. Group of answer choices make sense of memories retrieve memories pay attention to specific stimuli form new memories Use two variables k and total to write a for loop to compute the sum of the squares of the first 50 counting numbers, and store this value in total. Thus, your code should put 1*1 + 2*2 + 3*3 +... + 49*49 + 50*50 into total. Use no variables other than k and total. 16. Most aquatic animals excrete ammonia, while land animals excrete urea or uric acid. What is the most likely explanation for the difference? A. land animals cannot afford the energy needed to make ammonia B. they have different diets. C. ammonia is very toxic and it takes lots of water to dilute it. D. fish need to get rid of ammonia, but land animals need it to live E. land animals can get the extra energy needed to make urea or uric acid. Are these correct? If not help me please?? Why are strong acids also strong electrolytes? Also, is every strong electrolyte a strong acid? Consider the expression.6 60 63Which statements are true about the expression? Check all that apply.The 6 without an exponent is equivalent to the 6 having a 0 exponent.The sum of the exponents is 2.Multiply the exponents to simplify the expression.The expression has a value of1/36.An equivalent expression is 656-7. Patagonia managers look for employees who actively participate in the sport they design products for (i.e. a surfboard shaper has to love to surf). Requiring this passion and experience is part of the Classify a triangle with angle measures of 63 degrees and 27 degrees. Acute Obtuse Right Not Possible If the price of walnuts rises, many people would switch from consuming walnuts to consuming pecans. But if the price of salt rises, people would have difficulty purchasing something to use in its place. These examples illustrate the importance of How is Earth just the right size to support life?Please select all that apply.1.If Earth were much smaller than it is, it would not retain water, oxygen, or an atmosphere2.If Earth were much smaller than it is, it would have a thick atmosphere of ammonia and methane3.If Earth were smaller than it is, it would not have been able to retain the free oxygon in the atmosphere that allowed the first organisms to come into being4.If Earth were larger than it is, its gravity would be higher, and it would not retain water, oxygen, of an atmosphere5.If Earth were larger than it is, its gravity would be higher, resulting in a thick atmosphere of ammonia and methane Balanced forces keep this boy in place on his chair. Whatare the two equal and opposite forces occurring here?INILULU 2014 K. Wright Which set of ordered pairs represents a function? A {(22, 5), (23, 10), (22, 7), (23, 5)} B {(22, 5), (26, 10), (23, 7), (23, 5)} C {(22, 10), (23, 10), (24, 7), (25, 5)} D {(24, 10), (23, 6), (22, 7), (24, 5)} You have just made your first $4,000 contribution to your retirement account. Assume you earn a return of 14 percent per year and make no additional contributions. a. What will your account be worth when you retire in 25 years? (Do not round intermediate calculations and round your answer to 2 decimal places, e.g., 32.16.) b. What if you wait 10 years before contributing? (Do not round intermediate calculations and round your answer to 2 decimal places, e.g., 32.16.) 20 pts. The color of your eyes is an example of an inherited trait. These are the traits that are passed down to you from your parents. How are inherited traits as this passed from parents to their children? A)Traits like this are developed over a long period. B)Traits like this are responsible for the way you look, act, and feel. C)Traits like this are determined by the genes passed from parents to their children. D)Traits like this are determined by the knowledge passed from parents to their children. Joe is working on a design team that uses a computer-aided design (CAD) system. Joe has been complaining that it takes too long to perform tasks such as panning, rotating, and zooming. You have been asked to look at Joe's computer and to make any changes required to increase Joe's productivity. A small toy car draws a 0.50-mA current from a 3.0-V NiCd (nickel-cadmium) battery. In 10 min of operation, (a) how much charge flows through the toy car, and (b) how much energy is lost by the battery? 4. (Resistance and Ohms law, Prob. 17.16, 1.0 point) How Using the right-hand rule from your lessons, determine the directions of the electrical current and magnetic field of the electromagnet. Create an illustration of these perpendicular forces and include it below. (You can take a picture of your illustration or use an online drawing program to make your illustration.) Identify the type of star that goes through these steps in their life cycles.Formation of a protostar: Formation of a black hole: Formation of a white dwarf: Formation of a red giant star: Formation of a main sequence star: Although Justin spent his first 18 months in an orphanage, his adoptive mother believes sensitive caregiving will help Justin overcome his early experiences. Justin's mother emphasizes the role of __________ in development. Group of answer choices "As I realized that our right wing would no longer fly and I couldn't raise it, and was trying to hold left rudder and aileron, my left foot kept slipping off the rudder pedal," says Maxwell. "I looked down and said, Oh my God. My whole left leg and foot were covered with blood, and there was a pool of blood and it was all over that rudder pedal. And I knew Id been hit in the left side with shrapnel. But then I realized: It aint blood, its hydraulic fluid. "At no time did I feel heroic or any of that kind of stuff," he says. "Hell, I was scared. I didnt want to die, but I had to do whatever I needed to do. The thing that sticks out in my mind the most was when I realized we were going to be crashing into the Atlantic Ocean, and I thought we were goners. But in a last-minute desperate effort to avoid catastrophe, I kicked in full right rudder and threw the plane into a skid, and sure enough, instead of our cartwheeling and breaking up and exploding, the water put the fire out, and the airplane broke in three pieces, but it didnt explode or burn." Seven of the 10 crew members survived.