Energy, Work, Power and Efficiency

What is the difference between calculating power and work?

• Power takes into account the time it takes to complete a task
• Work takes into account the time it takes to complete a task
• Power is force/area
• Work is force/area

Bob (80 kg) uses 180 N of force to get him up the slope. The vertical distance is 2 m and the diagonal is 10 m. Calculate the work he does.

• 1600 J

• 160 J

• 3600 J

• 1800 J

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Which situation is work not done?

• lifting a 20 pound box off the floor
• holding a 20 pound box above the floor
• sliding a 20 pound box across the floor
• sliding a 20 pound box up an inclined plane

A battery converts what type of energy to another?

• sound to kinetic
• light to heat
• mechanical to electrical
• chemical to electrical

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Energy Efficiency is calculated by useful energy (Energy Out) divided by energy consumed (Energy In) , expressed as a percentage

• False

• True

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The SI Unit for Energy is

• Joule

• Newton

• Calorie

• Watt

What percent energy is wasted by a machine if the energy input is 262 J and the energy output is 131 J?

• 5%

• 50%

• 100 J

_______ is defined as the rate at which work is done.

• Efficiency

• Kinetic energy

• Potential energy

• Power

25 N force is applied to a box and box moves 10m. Find the work done by the force.

• 250J

• 25.48J

• 25N

• 2452.5J

An object has a weight of 200 N and is moved 3 meters.  How much work is done?

• 66.7 J
• 600 J
• 203 J
• 0.015 J

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