Work done, Power and Energy

A block of mass m is pulled over a distance d by an applied force F which is directed in parallel to the displacement. How much work is done on the block by the force F?

• mFs

• zero

• Fs

• –Fs

A spacecraft moves around Earth in a circular orbit with a constant radius. How much work is done by the gravitational force on the spacecraft during one revolution?

• Fs

• zero

• mgh

• ½ mv2

What happens to the total energy of a moving object if all the applied forces are conserved?

• It increases

• It decreases

• It remains constant

• The velocity is required to answer this question

At the beginning of a roller coaster ride, the roller coaster car has an initial energy mostly in the form of PE. Which statement explains why the fastest speeds of the car will be at the lowest points in the ride?

• At the bottom of the slope kinetic energy is at its maximum value and potential energy is at its minimum value

• At the bottom of the slope potential energy is at its maximum value and kinetic energy is at its minimum value

• At the bottom of the slope both kinetic and potential energy reach their maximum values

• At the bottom of the slope both kinetic and potential energy reach their minimum values.

The work–energy theorem states that the change in the kinetic energy of an object is equal to what?

• The work done on the object

• The force applied to the object

• The loss of the object’s potential energy

• The object’s total mechanical energy minus its kinetic energy

A car’s engine generates 100,000 W of power as it exerts a force of 10,000 N. How long does it take the car to travel 100 m?

• 1 s

• 0.1 s

• 10 s