Which best supports the idea that the surface of the moon has changed very little?

a) If photographs of the moon were taken millions of years ago, the surface would look the same.
b) Because the moon does not have a large iron core, it is not possible for geologic events to occur on the moon.
c) Because the moon has no atmosphere, it is not possible for geologic events to occur on the moon.
d) If one considers the history of the moon, there is only one distinct phase of its development.

The force required to accelerate a 0.75 kg ball at a rate of 25 m/s^2 is approximately 19 newtons, calculated using Newton's second law of motion.

To calculate the required force to make the ball accelerate at the given rate, we need to use Newton's second law of motion, which states that the force applied on an object is equal to its mass times its acceleration (F=ma). To find the force, we multiply the mass of the ball (0.75 kg) by the acceleration (25 m/s^2).

This gives us a force of 18.75 newtons. None of the provided options match this exact answer; the closest option is B. 19 newtons, so we would select this as the best answer with the understanding that it has been rounded.

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Answer:

.a 90 ft/sec     b. s=400ft

Explanation:

when an object is shot straight upward, the force of gravity which is the earth magnetic pull  on an object to its center, acts on it

The basic parameters to be considered are

a=-g, -32ft/sec

s=distance/height attained by the object during its motion against gravity

t=time ,secs

u=initial velocity

V=final velocity ft/sec

from newtons equation of motion,

a) V = u + g*t  

So V = 250+ -32*5= 90 ft/sec  

it's velocity after 5 seconds has elapsed is  90 ft/sec  

b) s = [tex]s=ut+\frac{1}{2} *at^{2}[/tex]

[tex]s=250*5+\frac{1}{2}-32 *5^{2}[/tex]

s=400ft

the height attained after 5 seconds. ..s=400ft

Power is the rate of work done. Less the power is less will be the work done or longer be the time period. Hence, same amount of work being done over a longer period of time.

Power is a physical quantity that describes the work done per unit time. Thus, power is the rate of work done. Work done on a body is equivalent to the energy of the body. Thus power is rate of energy too.

If a force applied on a body results in displacement, it is said to be work done on the body. The ratio of work done to the time is the power of the object.

P = w/t

Therefore, as the work done increases power increases. The more work done within short time, more will be the power. If the same amount of work being done over a long period of time, the object is having less power.

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Final answer:

Having less power implies performing the same amount of work over a longer period of time, as power is the rate of work done over time.

Explanation:

When discussing the relationship between work, power, and time, power is defined as the rate at which work is done or the amount of work per unit time. If we consider two scenarios where the same amount of work is done, the one with less power will require a longer period of time to complete the work. Therefore, having less power most likely means there is the same amount of work being done over a longer period of time.

By definition, of the law of ohm, we have to:

[tex] V = I * R
[/tex]

Where,

V: voltage

I: current

R: resistance

Therefore, we have that the relationship between voltage and current is proportional.

The proportionality constant for this case is the resistance.

For the current we have:

[tex] I = \frac{V}{R}
[/tex]

The proportionality constant for this case is the inverse of the resistance.

Answer:

A statement that describes the relationship of voltage and current is:

Voltage is directly proportional to current because I = V / R

Answer:

C nutcracker

Explanation:

A nutcracker is an example of a lever, which belongs to the second -class levers. It has the fulcrum at one end and the effort at the opposite end with the load i.e the nut at its middle. another example is a wheelbarrow.

The jackhammer produces primarily P-waves (compression waves) and S-waves (shear waves) that transfer energy into the ground, causing the pavement to break up. P-waves involve particle motion parallel to wave direction, while S-waves involve perpendicular particle motion. These waves are efficient in fracturing solid materials.

The vibrations produced by a jackhammer that are used to break up pavement generate seismic waves, specifically compression waves and shear waves.

A compression wave, also known as a P-wave (primary wave), is characterized by the motion of particles parallel to the direction of wave propagation. In other words, the material through which the wave passes is alternately compressed and expanded along the direction of the wave.

In contrast, a shear wave, or S-wave (secondary wave), involves particle motion that is perpendicular to the direction of wave propagation. This type of wave causes materials to move up and down or side to side.

When the jackhammer strikes the pavement, it primarily generates these two types of body waves, transferring energy into the ground to fracture and break up the solid material effectively.

Answer:

Total tension in the person's arm = 58.82 N

Explanation:

Normal Contact Force: Normal contact force is the vertical  component of the contact force that is perpendicular to the surface that an object makes contact with.

As shown in fig.1 in the diagram on the attached file below.

The Normal contact force (R) = Tsinθ = The vertical component of T

Where T = Total tension in the person's arm (N), θ = angle of inclination to the horizontal.

∴ R = Tsinθ

T = R/sinθ where R= 23N, θ =23°

T = 23/sin23° = 23/0.391

T = 58.82 N

∴ Total tension in the person's arm = 58.52 N

We have that from the Question, it can be said that  the total tension in the person's arms is

Ft=129N

From the Question we are told

A computer base unit of mass 7.5 kg is dragged along a smooth desk. If the normal contact force is 23N and the tension in the arm of the person dragging it acts at 23 degrees to the horizontal, then what is the total tension in the person's arms? ...?

Generally the equation for Horizontal motion is mathematically given as

[tex]\sumFx=FtCos \theta\\\\\sumFx=ma[/tex]

Generally the equation for vertical motion is mathematically given as

[tex]Ftsin\theta+fn=mh\\\\Therefore\\\\Ft=\frac{7.5*9.8-23}{sin23}[/tex]

Ft=129N

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Answer: detonation

detonation

Answer:[tex]510. 12 cm^3[/tex]

The volume of a cylindrical conduit, [tex]V=\pi (r_2^2-r_1^2) h[/tex]

where [tex]r_1[/tex] is the inner radius, [tex]r_2[/tex] is the outer radius, h is the length.

First of all, we would covert each parameter into centimeters.

length of the conduit, [tex] h=4 ft=4\times 30.48 cm=121.92 cm[/tex]

outer radius, [tex]r_1=2.2/2 in =1.1 in= 1.1\times 2.54 cm=2.79 cm[/tex]

inner radius, [tex]r_1=2/2 in =1 in= 2.54 cm[/tex]

Insert the values in the volume formula,

[tex]V=3.14 \times (2.79^2-2.54^2) \times 121.92 cm^3=510. 12 cm^3[/tex]

Hence, the volume of metal in the conduit is 510. 12 cubic centimeters.

Answer:

Option (b)

Explanation:

A nuclear reactor is a set up in which nuclear fission takes place and then the energy released is used to generate electrical energy.

Initially the nuclear energy is released by the fission of Uranium or reactor fuel.

Now, this nuclear energy is used to heat the water, then the energy from the hot water or steam is used to rotate the turbine, finally the turbine rotate and the electrical energy is generated by the generator.

So, the correct sequence is

nuclear energy - thermal energy - mechanical energy - electrical energy

Nuclear energy- thermal energy- mechanical energy-electrical energy.

The total amount of energy in the universe has never changed and will never change because it cannot be created or destroyed. This does not imply that energy cannot change forms or even move between objects though; it does.

Kinetic energy, or the energy attributed to motion, can be transferred from a moving item to a stationary object by means of effort, which is a frequent example of energy transfer that we experience in everyday life.

A portion of the kinetic energy in the club is transferred to the golf ball when it is struck by a stationary golf ball due to the "work" the club does on the ball.

Therefore, Nuclear energy- thermal energy- mechanical energy-electrical energy.

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The power that can be produced when the energy in a cup of ice cream is expended over a period of 10 minutes is approximately 1,394.67 watts or 1.87 horsepower.

To calculate the power that can be produced when the energy in a cup of ice cream is expended over a period of 10 minutes, we need to convert the energy from kilojoules (kJ) to joules (J). Given that each food Calorie is equal to 4,184 joules, a half-cup of ice cream contains about 836,800 joules (200 Calories × 4,184 joules/Calorie).

Next, we need to calculate the power. Power is calculated by dividing the energy by the time. So, the power that can be produced when the energy in a cup of ice cream is expended over a period of 10 minutes (600 seconds) is 1,394.67 watts (836,800 joules ÷ 600 seconds).

To convert the power from watts to horsepower, we need to divide the power by 745.7 (1 horsepower = 745.7 watts). Therefore, the power can be converted to approximately 1.87 horsepower (1,394.67 watts ÷ 745.7).

Correct answer choice is :

B) Scientific theories are never proven.

Explanation:

A scientific theory is a well-substantiated description of some features of the natural world, based on a body of evidence that has been frequently authenticated through investigation and experimentation. Such fact-supported hypotheses are not conclusions but authentic statements of the actual world. A scientific theory may be changed and eventually discarded if it cannot be done to fit the new conclusions in such conditions, a more precise theory is then needed.

Option (b) is correct. The scientific theories are the explanations that cannot be proven true.

Explanation:

The Scientific theories are basically the explanations given by the scientists based on the different physical appearances in the universe. The Scientific theories are given based on the patterns that have been occurring for years.

The examples of various scientific theories that are given on the Earth are the tectonic plates theory, Electromagnetic theory, theory of relativity etc. These theories are given by the scientists to explain several patterns that occur in nature.

These scientific theories have never been proven to be true but on the other hand there is no critic to question these theories. Therefore, they have been accepted universally until any proven fact denies them.

Therefore, the scientific theories can also be regarded as the explanations that are accepted universally without being proven because there has been no statement that explains against them.

Thus, Option (b) is correct. The scientific theories are the explanations that cannot be proven true.

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Answer Details:

Grade: High School

Subject: Physics

Chapter: Scientific laws and theories

Keywords:

scientific, theories, patterns, nature, explanation, prove, critic, against, tectonic plates, laws, statement.

Answer:

a) one substance must dissolve in another.    

Explanation:

A solution is mixture in which a substance (solid, liquid or gas) dissolves in a liquid. A salt dissolved in water is an example solid dissolved in liquid. Ammonia dissolved in water is an example of liquid in liquid and oxygen dissolved in water is an example gas dissolved in liquid.

The substance being dissolved is known as solute and the liquid in which solute is known as solvent.

Answer : t = 7.044 sec

Explanation :

It is given that,

Velocity, [tex]v=90\ feet/sec[/tex]

distance, [tex]s=160\ m[/tex]

[tex]H(t)=-16\ t^2+ vt+ s[/tex]

When firecracker hits the ground hen H(t) = 0

So, [tex]-16 t^2+90\ t+160=0[/tex]

or

[tex]8 t^2-45\ t-80=0[/tex]

Solving this quadratic equation, we get

[tex]t=\dfrac{-(-45) \pm \sqrt{(-45)^2-4(8)(-80)} }{2(8)}[/tex]

[tex]t=\dfrac{45\ \pm\sqrt{4585} }{16}[/tex]

[tex]t=7.044\ sec[/tex]

Neglecting negative values as time can't be negative.

Firecracker will take 7.044 sec to hit the ground.

Answer:

c)have insulator and conductor properties.

Explanation:

Semiconductors, as the name suggest have properties of both insulators and conductors. Until the current/voltage applied to them reaches a particular threshold they work like an insulator. Once the threshold is crossed they behave like a conductor. This property makes them very useful in electronic devices. In fact almost all the electronic equipment in today's age use semiconductors in some way or the other.

The Doppler effect says that the observed wavelength is shortened

when the source is approaching the observer, and lengthened when

the source is receding from the observer.

All we can say about the police car and its siren is that the sound/color

has a shorter wavelength as it approaches us, and a longer wavelength

as it recedes.

Any of these pairs of answers would say that:

  A -- A

  C -- A

  D -- A

or

  D -- D

For each of these pairs, the second wavelength is longer than the first one.

(We don't know which pair is the actual one, because we don't know the actual color of the police car.)

If we relate the Doppler effect on sound to the color of light waves, a police car would be the color blue as it approaches and the color red as it recedes away from the observer.

The Doppler effect is a phenomenon that occurs when two objects move closer or farther apart, increasing (or decreasing) the frequency of sound, light, or other waves.

The Doppler effect is to sound waves as well for the light waves

The apparent shift in the frequency of the light that the observer perceives as a result of relative motion between the source of the light and the observer is known as the Doppler effect of light.

However, the equations for the Doppler shift for sound waves vary significantly depending on whether the source, the observer, or the air is moving. Light doesn't need a medium to travel, and the observer and source's relative speeds are the only factors affecting the Doppler shift for light.

A police car would appear blue as it approaches as there is an increase in frequency resulting in the decrease in the wavelength of light known as the blue shift.

similarly, it appears red as it moves away from the observer because of the decrease in the frequency resulting increase in the wavelength of the light known as the redshift.

Thus, If the Doppler effect on sound may be compared to the color of light waves, then a police car would appear blue as it approaches and red as it moves away from the observer.

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According to Hooke's Law, the distance when a spring is stretched by a hanging object varies directly as the weight of the object. We can use this information to find the distance when the weight is 7 kg. We get 84 cm.

Hooke's Law states that the distance d when a spring is stretched by a hanging object varies directly as the weight w of the object.

This means that if you double the weight, the distance will also double.

Mathematically, we can express this relationship as d = kw, where k is the constant of variation.

To find the value of k, we can use the given information: when the weight is 3 kg, the distance is 38 cm.

Plugging these values into the equation, we get 38 = 3k.

Solving for k, we divide both sides by 3 to get k = 12.

Now, we can find the distance when the weight is 7 kg by plugging this value into the equation: d = 12 * 7 = 84 cm.