Conservation of momentum and energy: Self Test

A man drops a 10-kg rock from the top of a 5-meter ladder

1 pts

Assuming that air friction is negligible, how much kinetic energy does it have when it hits the ground? Calculate the answer yourself if you can.

Hint: First Calculate the potential energy at the top

Potential energy at top = weight • height

Remember weight = mass • gravity = mg

PE = mg • height

PE = (1) kg • (2) m/s² • (3) m
PE = (4) (kg • m/s²) • m
PE = (5) newton • m
PE = (6) joules

What is the speed of the rock just before it hits the ground (approximate your answer)? (7) m/s

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Explanation

Impulse and momentum are related

1 pts

volume_mute

as impulse applied to an object is equal to the change in momentum of the object

True

False

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How does the momentum of a bullet as it leaves the barrel of a gun compare to the recoil momentum of the gun?

1 pts

volume_mute

The two momenta are equal (but opposite in direction)

The two momenta are not equal and not opposite in direction

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A moving object collides with a stationary one

1 pts

volume_mute

Suppose a moving object collides with a stationary one and the two stick together. How will the speed of the stuck-together objects compare to the speed of the original moving object?

It will be more

It will be less

It will be equal

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Is momentum a scalar or a vector quantity?

1 pts

volume_mute

Scalar

Vector

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Two blocks of ice are sitting on a table with a piece of dynamite between them

1 pts

One block of ice has a mass of 12 Kg and the other's mass is 18 kg. The dynamite explodes. If the block of lesser mass moves off with a speed of 10 m/s, what is the speed of the more massive block?

(1) m/s

Please type in the answer as it is wither it has a negative sign or not

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A 2000-pound car moving at 50 miles per hour collides with a stationary car weighing 3000 pounds

1 pts

If the two cars stick together, what is their speed immediately after the collision?

Hint: On both sides of the equation, you may use "pounds" for mass and "miles per hour" for velocity. This is permissible because weight (pounds) is proportional to mass, and miles/hour is a legitimate unit of velocity.)

(1) miles/hour

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Is the law of conservation of momentum violated if a gun is attached so firmly to a support that it cannot recoil?

1 pts

volume_mute

Yes

No

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Work is the product of the force exerted and the distance through which it is exerted

1 pts

volume_mute

True

False

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Holding a piano at shoulder

1 pts

volume_mute

How much work is done in holding a piano at shoulder height for 15 minutes if the piano weighs 1200 newtons and your shoulder is 1.5 meters above the ground?

1800 joule

450 joule

27000 joule

No work is done

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Power is work done multiplied by the time used in doing the work

1 pts

volume_mute

True

False

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As an object falls toward the ground, what happens to its potential energy?

1 pts

volume_mute

It increases

It decreases

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Suppose two objects have the same mass, but one is moving twice as fast as the other

1 pts

volume_mute

The kinetic energy of the fast one is how many times as great as the kinetic energy of the slow one?

two times

three times

four times

five times

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What happens to the kinetic energy of an object as the object falls?

1 pts

volume_mute

It increases

It decreases

Nothing happens to it

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How does a perfectly elastic collision differ from an inelastic collision?

1 pts

In (1), kinetic energy is conserved, but in (2), it is not.

Please drag and drop the selected option in the right place or type it instead

a perfectly elastic collision

an inelastic collision

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Lifting a 5-kg object 3 meters requires how much energy?

1 pts

(1) joules

approximate your answer without decimal points

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what is the power of the lifter if it requires 147 joules to lift an object above the ground for 2 seconds?

1 pts

(1) watts

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An object is going 10 m/s when it hits the ground.

1 pts

From how high did it fall?

(1) meters

Hint: Since the object's mass does not matter, you may choose any mass you want. and do not forget to approximate to the nearest first decimal point.

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A man drops a 10-kg rock from the top of a 5-meter ladder

Correct Answer

Explanation

Impulse and momentum are related

Correct Answer

Explanation

How does the momentum of a bullet as it leaves the barrel of a gun compare to the recoil momentum of the gun?

Correct Answer

Explanation

A moving object collides with a stationary one

Correct Answer

Explanation

Is momentum a scalar or a vector quantity?

Correct Answer

Explanation

Two blocks of ice are sitting on a table with a piece of dynamite between them

Correct Answer

Explanation

A 2000-pound car moving at 50 miles per hour collides with a stationary car weighing 3000 pounds

Correct Answer

Explanation

Is the law of conservation of momentum violated if a gun is attached so firmly to a support that it cannot recoil?

Correct Answer

Explanation

Work is the product of the force exerted and the distance through which it is exerted

Correct Answer

Explanation

Holding a piano at shoulder

Correct Answer

Explanation

Power is work done multiplied by the time used in doing the work

Correct Answer

Explanation

As an object falls toward the ground, what happens to its potential energy?

Correct Answer

Explanation

Suppose two objects have the same mass, but one is moving twice as fast as the other

Correct Answer

Explanation

What happens to the kinetic energy of an object as the object falls?

Correct Answer

Explanation

How does a perfectly elastic collision differ from an inelastic collision?

Correct Answer

Explanation

Lifting a 5-kg object 3 meters requires how much energy?

Correct Answer

Explanation

what is the power of the lifter if it requires 147 joules to lift an object above the ground for 2 seconds?

Correct Answer

Explanation

An object is going 10 m/s when it hits the ground.

Correct Answer

Explanation

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