Work Force and Motion

A girl kicks a soccer ball into the air. Which of these best explains why the soccer ball falls back to Earth?

• The acceleration of the ball is unstable.

• The motion of the ball is changed by external forces.

• The force exerted on the ball is greater than gravity.

• The pressure on the ball changes with altitude.

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Which of Newton's laws of motion is defined?

• 1st

• 2nd

• 3rd

• 4th

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The amount of work necessary to move a dirt pile was 620 J. The amount of force used to move the dirt pile was 28.2 N. How far was the dirt pile moved?

• 28 m

• 17,484 m

• 13,640 m

• 22 m

If it takes a force of 2000 N to move a crate at a rate of 3.4 m/s2, what is the mass of

the object?

• 6,800 kg

• 588.2 kg

• 294.1 kg

• 13,600 kg

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It took a bulldozer 62,000 J of work to move a rock 30 meters. How much force did the bulldozer have to apply?

• 2.1 N

• 206.7 N

• 186000 N

• 2066.7 N

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A force of 100 N acts upon an object with a mass of 75 kg. What is the object's

acceleration?

• 1.3 m/s2

• 7,500 m/s2

• 130 m/s2

• 0.75 m/s2

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To complete a project, 200,000 Joules of work are needed. The time taken to complete the project is 20 seconds. How much power is needed?

• 1,000,000 J/s

• 10,000 J/s

• 0.0001 J/s

Which is the result of using a more powerful motor to run an elevator?

• The same amount of work is done in less time.

• Less work is done in the same amount of time.

• The same amount of time is needed to move the same distance.

• A longer time is needed to move a shorter distance.

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A car manufacturer reduces the mass of a car by 250 kg. If the new design is

otherwise identical to the old design, how will the new car compare to the old car?

• It will release more gas emissions.

• It will have a greater gravitational attraction to the road.

• It will require more fuel to operate.

• It will need less force to move.

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All of the following forces decrease the acceleration of a basketball rolling across the

court EXCEPT —

• rolling friction

• fluid friction

• static friction

• gravity