DOING WORK AND POWER E0

A force of 5.0 N acts on an object for 4.0 s. The object moves a distance of 8.0 m in the direction of the force. What is the work done by the force?

• 20 J

• 40 J

• 32 J

• 10 J

A box of mass 8.0 kg is lifted vertically from the ground on to a shelf that is 2.0 m above the ground. The gravitational field strength g is 10N/kg. How much work is done as the box is lifted on to the shelf?

• 160 J

• 80 J

• 16 J

• 8 J

The diagram shows a box of weight 400 N being pulled up a frictionless slope by a force. How much work is done against gravity in moving the box from X to Y?

• 2000 J

• 1600 J

• 1200 J

• 4000 J

A force acts on an object and moves it a certain distance in the direction of the force. The force is now doubled and the distance increases by a factor of 2. What happens to the work done by the force on the object?

• It increases by a factor of 1.5.

• It doubles.

• It increases by a factor of 4.

• It increases by a factor of 6

A force acting on an object increases the kinetic energy of the object from 20 J to 80 J in 5.0 s What is the average power produced by the force?

• 12 W

• 6 W

• 12 J

• 6 J

Two workers are stacking cans on to a shelf in a shop. The workers lift the same number of identical cans on to the same shelf from the same level. Worker P takes 3.0 minutes to lift the cans. Worker Q takes 4.0 minutes to lift the cans. Which statement about the workers is correct?

• Worker P develops less useful power than worker Q.

• Worker P develops more useful power than worker Q.

• Worker P does less useful work than worker Q.

• Worker P does more useful work than worker Q.

Which quantities are measured in the same unit?

• energy, power and work

• energy and power, but not work

• energy and work, but not power

• power and work, but not energy

Choose the correct answer

• A

• B

• C

• D

Choose the correct answer

• A

• B

• C

• D

A car accelerates uniformly from rest along a horizontal road. After 4.0s, its kinetic energy is 100 kJ. What is the useful power produced by the engine of the car?

Answer: ___________ (unit kW)