Energy Unit Test

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A force moves an object in the direction of the force. This graph shows the force versus the object’s position. Find the work done when the object moves from 0 to 10 m. Your first question?

• 100 J
• 200 J
• 300 J
• 600 J

Can work be done on a system if there is no motion?

• Yes, if an outside force is provided.
• Yes, since motion is only relative.
• No, since a system that is not moving has no energy.
• No, because of the way work is defined.

If you push twice as hard against a stationary brick wall, the amount of work you do

• Doubles
• is cut in half
• remains constant but non-zero
• remains constant at zero

An acorn falls from a tree. Compare its kinetic energy KE, to its potential energy, GPE.

• KE increases and GPE decreases.
• KE decreases and GPE decreases.
• KE increases and GPE increases.
• KE decreases and GPE increases.

By what factor does the kinetic energy of a car change when its speed is tripled?

• no change at all
• factor of 3
• factor of 6
• factor of 9

Two paths lead to the top of a big hill. One is steep and direct, while the other is twice as long but less steep. How much more potential energy would you gain taking the longer path?

• the same
• twice as much
• half as much
• you gain no PE in either case

How does the work needed to stretch a spring 2 cm compare to the work needed to stretch it 1 cm?

• same amount of work
• twice the work
• 4 times the work
• 8 times the work

A mass attached to a vertical spring causes the spring to stretch and the mass to move downwards. What can you say about the spring’s potential energy (EPE) and the gravitational potential energy (GPE) of the mass?

• both EPE and GPE decrease
• EPE increases and GPE decreases
• both EPE and GPE increase
• EPE decreases and GPE increases