Energy, Work, and Power

Which of the following is a true statement about work?

• It measures how quickly an object accelerates 
• It measures how much effort is applied over a certain distance
• It measures the change in an object's rate of speed
• It measures how much time it takes to move a massive object

A weightlifter lifts two 300 newton weights 1.5 meters off the ground. How much work has he done?

• 600 J 
• 660 J
• 900 J 
• 1200 J 

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Simple machines make work easier by increasing what?

• The distance over which work is done 
• The force needed to do work 
• The time required to do work
• The acceleration of a massive object 

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You do 90 joules of work in 30 seconds. How much power have you generated?

• 30 watts
• 3 watts
• 120 watts
• 270 watts

You move a 0.8 kg object five meters in 4 seconds. How much power have you generated?

• 160 watts

• 10 watts

• 6.4 watts

• 17 watts

Which of the following would produce the most power?

• A mass of 10 kilograms lifted 10 meters in 10 seconds 
• A mass of 10 kilograms lifted 10 meters in 5 seconds
• A mass of 5 kilograms lifted 10 meters in 5 seconds
• A mass of 5 kilograms lifted 5 meters in 10 seconds

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An object has 12.4 J of potential energy and 23.5 J of kinetic energy. What is the mechanical energy of the system?

• 11.1 J

• 1.895 J

• 35.9 J

• 291.4 J

If two rocks are launched through the air at the same speed, but one has twice as much mass as the other, how do their kinetic energies compare?

• The kinetic energy of the two rocks is the same because they have the same speed

• The rock with the greater mass will only move a small distance and then fall straight to the ground

• The two rock could not have the same speed if they have different masses

• The rock with the greater mass has more kinetic energy than the rock with less mass even though they are traveling at the same speeds because both mass and speed affect kinetic energy.

Which point has the most kinetic energy?

• Ball G

• Ball F

• Ball E

• Ball D

• Ball A

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As a pendulum swings from its highest to lowest position, what happens to its kinetic and potential energy?

• Both the potential energy and kinetic energy decrease

• The potential energy decreases while the kinetic energy increases

• The kinetic energy decreases while the potential energy increases

• Both the potential energy and kinetic energy increase

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