Chapter 4: Work and Energy

In which of the following situations do your arms do work on books?

• dropping a stack of books onto a table
• carrying a heavey stack of books
• holding a heavy stak of books while standing
• picking up a pile of books from the floor

How much ork is done lifting a 9.10 kg box straight up onto a shelf that is 1.80 m high?

• 16 J
• 50 J
• 160 J
• 5 J

A 10 kg box sits on the floor. Approximately how high would you have to lift the box to increse gravitational potentila energy by 350 J?

• 15 m
• 7.0 m
• 3.6 m
• 35 m

As you throw a ball, you exert a force on that ball of 4.2 N. You exert this force on the ball while the ball moves a distance of 0.50 m. The ball then leaves your hand and travels a horizontal distance of 8.5 m to your friend. How much work have you done on the ball?

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IL.NGSSDCI.SCI.MS-PS3-5

It takes 600 J of work to lift a crate straight up but 1200 J to push that crate up a ramp to same height. What is the efficiency of the ramp?

• 30%
• 75%
• 50%
• 200%

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NGSS.MS-PS3-4

NGSS.MS-PS3-5

Compare the output force with the input force for a machine that has a mechanical advantage that is greater than one.

• The output force is equal to the input force
• More information is needed.
• The output force is greater than the input force
• The output force is less than the input force

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NGSS.MS-PS2-1

NGSS.MS-PS2-2

An input force of 80 N is used to lift an object weighing 240 N with a system of pulleys. What is the mechanical advantage of the pulley system?

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NGSS.MS-PS2-2

Using the scientific definition, which statement is always true of work?

• It is difficult
• It involves levers
• It involves a transfer of energy
• It is done with a machine

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NGSS.MS-PS3-1

NGSS.MS-PS3-4

NGSS.MS-PS3-5

The kinetic energy from an object's motion always changes when which factor changes?

• the objects volume
• the object's speed
• the object's direction of motion
• the object's chemical potential energy

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NGSS.MS-PS3-1

What is the gravitational potential energy of an Earth-dictionary system if the dictionary has a mass of 5.0 kg and is located 2.0 m above the ground? use the ground as the reference level.

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NGSS.MS-PS3-2