To find the number of revolutions a wheel makes after a torque is removed, calculate the angular velocity after torque application, then the angle of rotation during acceleration and uniform motion periods, and sum these angles. Convert the total angle in radians to revolutions by dividing by 2π.
Explanation:To calculate the number of revolutions a wheel makes after a torque is removed, you need to consider both the angular acceleration while the torque was applied and the subsequent angular velocity for the remainder of the time. The wheel starts from rest, so the initial angular velocity (ω0) is zero. During the first 4 seconds, the wheel undergoes angular acceleration (α) due to the torque, after which the wheel continues to rotate at the angular velocity it reaches at the end of 4 seconds. It is given that the angular acceleration is 2 rad/s².
First, find the angular velocity after 4 seconds using the formula ω = ω0 + αt, which gives ω = 0 + (2 rad/s²)(4 s) = 8 rad/s. This is the constant angular velocity for the next 11 seconds since there is no more torque applied.
To solve for the angle (θ) in radians that the wheel has turned during the full 15 seconds, use the equation for angular motion, θ = ω0t + ½αt², for the first 4 seconds and θ = ωt for the last 11 seconds. These are the angles during the intervals of constant acceleration and constant angular velocity respectively. Then, θ = (1/2)(2)(4²) rad during the acceleration and θ = (8 rad/s)(11 s) during uniform rotation. The total angle in radians is then the sum of the angles for the two intervals.
Since 1 revolution is 2π radians, divide the total angle in radians by 2π to find the total number of revolutions.
Which identifies an electrically neutral atom that gains electrons?
A.
negative ion
B.
positive quanta
C.
positive photon
D.
negative isotope
When an object that has been thrown into the air reaches its maximum height, which is true?
a. its velocity is zero. b. it is at its terminal velocity. c. it is not in free fall. d. its acceleration is zero.
Answer:
a. its velocity is zero.
Explanation:
At maximum height no activities is going on that is the velocity becomes zero because no movement occurs at that point
Since there is no moveent the velocity is zero.
At an object's maximum height in projectile motion, its velocity is zero but its acceleration due to gravity remains constant. Therefore, the correct statement is option a).
Here is the detailed reasoning:
An object thrown upwards will decelerate due to gravity until its velocity becomes zero at the maximum height. This is the point where its upward motion stops, and it is about to start descending.
The velocity magnitude at maximum height is zero, but its acceleration is still the acceleration due to gravity (g), acting downwards. Therefore, option d. its acceleration is zero, is incorrect.
Terminal velocity refers to the constant speed that a free-falling object eventually reaches, which is not relevant here. So, option b is incorrect.
Even at its maximum height, an object is still under the influence of gravity, meaning it is in free fall, which makes option c incorrect.
Therefore, the correct answer is a. its velocity is zero.
Which of the following frictionless ramps (A, B, or C) will give the ball the greatest speed at the bottom of the ramp? Explain.
The frictionless ramp A will give the ball the greatest speed at the bottom of the ramp.
What is speed?Speed is defined as the rate of change of the distance or the height attained. it is a time-based quantity. it is denoted by u for the initial speed while u for the final speed. its si unit is m/sec.
The potential energy is due to the virtue of the position and the height. The unit for the potential energy is the joule. Ball has the most potential energy due to her position at C.
The potential energy is mainly dependent upon the height of the object.
Potential energy = mgh
The potential energy gets converted into kinetic energy at the bottom. If the ramp is frictionless the potential energy completely gets converted into kinetic energy.
The kinetic energy results in the motion of the body.
Hence frictionless ramp A will give the ball the greatest speed at the bottom of the ramp.
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a uniform rope of length l is pulled by a constant force F.what is the tension in the rope at a distance l from the end, where it is applied?
...?
Which stage comes first in the life cycle of a high-mass star?
A. red giant
B. white dwarf
C. protostar
D. supernova
...?
Answer:
C. protostar
Explanation:
Due to the effect of gravity the hydrogen atoms are pulled together from the nebula. At this stage the star is not hot enough to start the nuclear fission. At this stage a star is called protostar. Eventually it will grow in size by attracting more hydrogen. When the temperature at the core is increased enough due to the gravitational pressure at the core of the star, then nuclear fission will start
what is junction resistance?
...?
what force is directly related to number of electrons?
Sometimes at a child's birthday party someone will rub a balloon on another's head and stick the balloon to the wall. this works because
a.the wall and balloon have the same charge.
b.the balloon has less weight because it has become charged.
c.the balloon discharges current into the wall and the wall becomes charged just like the balloon was.
d.the wall and the balloon have opposite charges and this creates an attractive force between the wall and the balloon.
T object]user: a ____ farm can be used to generate electricity
If a car is traveling 40 mph, how far will it go in 5 hours?
a. 100 miles
b. 200 miles
c. 80 miles
d. 800 miles
What is the speed of a wave that has a frequency of 45 Hz and a wavelength of 0.1 meters?
A. 0.45 m/s
B. 4.5 m/s
C. 45 m/s
D. 450 m/s ...?
Answer:
4.5
Explanation:
yes
why do all freely falling objects have the same acceleration
If a car is traveling westward with a constant velocity of 20m/s, what is the net force acting on the car
To calculate the velocity of an object, the _________ of the position vs time graph should be calculated.
By definition we have to:
[tex] v = \frac{dr}{dt}
[/tex]
Where,
dr / dt: rate of change of the position of an object with respect to time
Therefore, we know that in a position graph with respect to time, both variables are proportional.
The proportionality constant is the speed of the object.
Mathematically, this constant represents the slope of the line.
Answer:
To calculate the velocity of an object, the slope of the position vs. time graph should be calculated.
Why do the elements in group 16 share similar chemical properties?
Air pressure decreases as
a.
velocity increases.
b.
elevation increases.
c.
acceleration decreases.
d.
gravity increases.
Pressure can be measured in units of
a.
newtons.
b.
newtons per square meter.
c.
newtons per centimeter.
d.
newtons per cubic centimeter.
If a ball is thrown into the air with a velocity of 42 ft/s, its height (in feet) after t seconds is given by y = 42t − 16t2. Find the velocity when t = 1.
The velocity of a ball at t = 1 second when it was thrown up with an initial velocity of 42 ft/s, we differentiate the height function to get the velocity function and substitute t = 1 to find the velocity to be 10 feet per second.
The velocity of a ball thrown straight up into the air at a specific time (t = 1 second), using the given position function y = 42t - 16t². To find the velocity at t = 1, we differentiate the position function with respect to time to get the velocity function v(t) = dy/dt. After differentiation, we get v(t) = 42 - 32t and then plug in t = 1 to find the velocity at that moment.
After substituting t into the velocity function, we get v(1) = 42 - 32(1) = 10 ft/s. Hence, the velocity of the ball at t = 1 second is 10 feet per second.
How much power does a toaster have if it does 21,000 joules of work in 30 seconds?
The power of the toaster, calculated using the formula P = W/t, is 700 Watts.
Explanation:The power of an appliance like a toaster can be calculated using the formula for power which is P = W/t, where P is Power, W is work done or energy consumed, and t is time.
Given that the toaster does 21,000 Joules of work or consumes 21,000 joules of energy in 30 seconds, the power would thus be calculated as follows: P= 21,000J / 30 s. This equals 700 Watts. So, the toaster has a power of 700 Watts.
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Need help with science!
Which of the following statements about radioactive decay is true?
a. radioactive decay is the rate at which new atoms form.
b. During radioactive decay, atoms break down, releasing, particles or energy.
c. the rate of decay of a radioactive element cannot be approximated.
d. the number of radioactive atoms in a sample will always remain constant.
Which of the following terms refers to the time it takes for one-half of the radioactive atoms in a sample of a radioactive element to decay?
a. relative age.
b. absolute age.
c. potassium-argon date
d. half-life
Answer:
1. B
2. D
Explanation:
1. Radioactive decay occurs when a radioactive particle cannot maintain a high energy state due to its own weight. When a radioactive element (eg. Uranium) undergoes radioactive decay, its product/s (following the previous example, Uranium decays into Thorium) are more stable than its reactants.
The question might remain that after Uranium decays to Thorium, where does the extra mass go? The extra mass is released as an alpha particle, and through this process, a lot of energy is released as gamma radiation.
Hence, the answer is:
During radioactive decay, atoms break down releasing particles or energy.
2. The half-life of an element is referred to as:
The length of time taken for one half of the radioactive atoms in a sample to decay.
Hence, since the question states the definition of a half-life, the answer is D.
The correct answer is (b) 'During radioactive decay, atoms break down, releasing particles or energy.' And, the term for the time it takes for one-half of the radioactive atoms in a sample to decay is (d) 'half-life.'
Explanation:The true statement about radioactive decay is option (b), 'during radioactive decay, atoms break down, releasing particles or energy.' Radioactive decay is a spontaneous process where an unstable atomic nucleus loses energy by emitting radiation, such as an alpha particle, beta particle with neutrino or only a neutrino with case of Electron Capture, or a gamma ray. The other options do not accurately describe this process.
The term referring to the time it takes for one-half of the radioactive atoms in a sample of a radioactive element to decay is option (d), 'half-life.' Half-life is commonly used in nuclear physics and chemistry, and it provides us with a measure of the time scale on which radioactive decay processes occur.
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A window washer stands on a scaffolding 30 meters above the ground. If he did 23,520 joules of work to reach the scaffolding what is his mass
The mass of the window washer who stands on a scaffolding 30 meters above the ground is 78.4 Kg.
What is Potential Energy?Energy of the body due to its position with respect to some other object (say earth) is called potential energy.
Given is a a window washer who stands on a scaffolding 30 meters above the ground.
The amount of work done by the window washer will be stored inside him in the form of potential energy. Therefore, we can write -
mgh = 23520
m x 10 x 30 = 23520
m = 23520/300
m = 78.4 Kg
Therefore, the mass of the window washer who stands on a scaffolding 30 meters above the ground is 78.4 Kg.
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An amount of nitrogen undergoes a physical change and increases its volume. What can be known about this physical change?
The boiling point of the nitrogen increased.
The mass of nitrogen increased.
The color changed.
The density changed.
Correct answer choice is :
D) The density changed.
Explanation:
Density is the number of mass placed in a particular volume. The density of an object can vary if either the mass or volume of the object is modified. Fluids, such as water, have a specific density. If an object is thicker than water, it will sink; if it is less thick than water, it will float. Maximum material rises in volume when it gets hotter. For instance, if an iron rod is ignited, it will get longer and thicker and its density will reduce. This occurs because the mass of the rod stays the equivalent, but its volume rises.
During which type of change can an atom of one element transform into an atom of a different element
Answer:
Nuclear
Explanation:
a 700 kg racecar slowed from 30 m/s to 15 m/s. What is the change in momentum
Tim's car breaks down just down the street from his house. he and his friends decide to try to push it to his house. using newton's three laws of motion, explain why this will be difficult.
The friends have to combine their forces to be greater than the force of the car pushing back on them (3rd law). The car will remain at rest until an outside force acts on it that it is greater than its own (1st). The speed in which the car is being moved is directly related to the amount of force and direction of the kids pushing the car (2nd).
In which state of matter are the particles CLOSEST together?
A)
gas
B)
solid
C)
liquid
D)
plasma
In the solid state of matter, the particles are closest together. Thus, the correct option is B.
What are the states of matter?The state of matter is one of the distinct forms in which the matter can exist in nature. Four states of matter which are observable in the everyday life are solid, liquid, gas, and plasma states.
Solid state of matter is a state in which the particles are packed tightly in space. The constituent particles can be atoms or the solid particles. The intermolecular distances between the solid particles in the lattice are short and hence the forces of attraction between the molecules are strong. Solids are divided into three broad classes which are crystalline, non-crystalline (amorphous), and quasi-crystalline. Crystalline solids have a very high degree of order in a periodic atomic arrangement of molecules.
Therefore, the correct option is B.
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A construction worker runs a jack hammer for 1.5 hours. The jack hammer has 2.4 kilowatts of power. How much electrical energy does the construction worker use running the jack hammer?
A. 3.6 kilowatt-hours
B. 3600 kilowatt-hours
C. 0.625 kilowatt-hours
D. 1.6 kilowatt-hours
The energy used by the construction worker running the jackhammer for 1.5 hours, which has a power of 2.4 kilowatts, is calculated as 3.6 kilowatt-hours, which is answer choice A.
The energy used by the construction worker while running the jackhammer can be calculated using the formula for electrical energy, which is:
E = Pt
Where:
E is the energy in kilowatt-hours (kWh),P is the power in kilowatts (kW),t is the time in hours (h).Given:
P = 2.4 kW (power of the jackhammer),t = 1.5 hours (duration of use).Therefore, substituting the values we get:
E = 2.4 kW * 1.5 h = 3.6 kilowatt-hours
The correct answer is A. 3.6 kilowatt-hours.
A certain planet has an escape speed . If another planet has twice size and twice the mass of the first planet, its escape speed will be
A) Sqrt[2] V
B) V
C) V/2
D) V/Sqrt[2]
E) 2V
Answer:
answer is V
Explanation:
An object has a mass of 8.00 kg. What is the gravitational force on the object by the earth?
The gravitational force (weight) of an 8.00 kg object on Earth is 78.4 N. This is calculated using the formula 'w = mg', with 'g' being the Earth's acceleration due to gravity (9.80 m/s²).
Explanation:The gravitational force exerted on an object by the Earth (also known as the object's weight) can be calculated using the formula w = mg, where m is the mass of the object and g is the acceleration due to gravity. On Earth, the acceleration due to gravity (g) is approximately 9.80 m/s².
For an object with a mass of 8.00 kg, the gravitational force (weight) would be calculated as follows:
w = mg = (8.00 kg)(9.80 m/s²) = 78.4 N
Thus, the Earth exerts a gravitational force of 78.4 N on an object with a mass of 8.00 kg.
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Why do magnetic lines of forces make a closed loop?
Planet a has three times the mass of planet b and the same radius. from this information, what can we conclude about the acceleration due to gravity at the surface of planet a compared to that at the surface of planet b?