D - Work and Power

Question 1

Calculate the potential energy gained when a 70kg person climbs a height of 8m

Answer 1

PE = mgh PE = 70 x 10 x 8 = 5600 J

Question 2

State the equation for Gravitational Potential Energy

Answer 2

GPE=mgh

Question 3

A lift motor converts 90000 J into potential energy by raising the lift through a height of 6m. Calculate the mass lifted.

Answer 3

PE = mgh m = PE/gh m = 90000 / 10 x 6 m = 90000 / 60 = 1500kg

Question 4

Calculate the potential energy gained when a 70kg person climbs a height of 6m.

Answer 4

PE = mgh PE = 70 x 10 x 6 = 4200 J

Question 5

A lift motor converts 150000 J into potential energy by raising the lift through a height of 8m. Calculate the mass lifted.

Answer 5

PE = mghm = PE/ghm = 150000 / 10 x 8m = 150000 / 80= 1875 kg

Question 6

A crate is pushed across a floor by a force of 80N. How much work is done in moving the crate 6m?

Answer 6

WD = F x d WD = 80 x 6 = 480 J

Question 7

A car moves at a constant speed. How far will it travel if the engine is exerting a constant force of 3000N and the energy transferred is 200000J?

Answer 7

WD = F x d d = WD/F d = 200000 / 3000 = 66.67 m

Question 8

A crate is pushed across a floor by a force of 70N. How much work is done in moving the crate 12m?

Answer 8

WD = F x d WD = 70 x 12 = 840 J

Question 9

A car moves at a constant speed. How far will it travel if the engine is exerting a constant force of 5000N and the energy transferred is 1000000J?

Answer 9

WD = F x d d = WD/F d = 1000000 / 5000 = 200 m