Test Review

A bicyclist climbs a hill at a constant speed of 2.5 meters per second (m/s) by applying an average force of 85 Newtons (N). Approximately how much power does the bicyclist develop?

• 212 Watts

• 1115 Watts

• 100 Watts

• 2450 Watts

Answer explanation

Power can be calculated by Work/time and Force*velocity

The diagram below shows a 1.0 kilogram (kg) sphere at point A on an incline. The sphere has a potential energy of 5.0 Joules (J) with respect to the base of the incline. What is the potential energy of the sphere when it rolls to point B halfway down the incline?

• 0

• 2.5

• 3

• 5

A 110 kilogram (kg) bodybuilder and his 55 kilogram (kg) friend run up identical flights of stairs. The bodybuilder reaches the top in 4.0 seconds (s) while his friend takes 2.0 seconds (s). Compared to the power developed by the bodybuilder while running up the stairs, the power developed by his friend is which of the following? (take g as 10m/s²)

• twice as much

• the same

• half as much

• four times as much

A college student has just bought a small computer that weighs 50 Newtons (N). To reach her apartment on the 5^th floor, which is 35 meters (m) up, she must climb the stairs. How much work must she do to take her computer up the stairs?

• 15 joules

• 50 joules

• 85 joules

• 1750 joules

Which of the following graphs best represents the relationship between the power required to raise an elevator and the speed at which the elevator rises?

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The graph represents the relationship between the work done by a student running up a flight of stairs and the time of ascent. What does the slope of the graph represent?

• speed

• power

• impulse

• momentum

Which of the following carts has the greatest kinetic energy?

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Answer explanation

Calculate kinetic energy with KE=0.5*mass*velocity^2

Student A lifts a 50 Newton (N) box from the floor to a height of 0.4 meter (m) in 2.0 seconds (s). Student B lifts a 40 Newton (N) box from the floor to a height of 0.5 meter (m) in 1.0 second (s). Which of the following is true?

• Student B does the same amount of work as student A but develops less power.

• Student B does the same amount of work as student A but develops more power.

• Student B does more work than student A but develops less power.

• Student B does less work than student A but develops more power.

The diagram below represents a 5 kilogram (kg) cart in motion at the foot of a hill 10 meters (m) high. For the cart to reach the top of the hill, what is the minimum kinetic energy the cart must possess in the position shown (take g as 10m/s²)?

• 5 joules

• 50 joules

• 250 joules

• 500 joules

A girl weighing 500 Newtons (N) takes 50 seconds (s) to climb a flight of stairs 18 meters (m) high. How much power does the girl develop?

• 180 watts

• 1400 watts

• 4000 watts

• 9000 watts