In which situations is work being done? ( you can pick more than 1) hannah leans against her locker, but it doesn’t move. andy’s car rolls down a hill with the engine off. a wind turbine stands still on a sunny, windless day. a balloon expands as it is heated by the sun. james pedals a stationary exercise cycle that doesn’t move.

Andy’s car rolls down a hill with the engine off.

A balloon expands as it is heated by the Sun.

James pedals a stationary exercise cycle that doesn’t move.

Explanation:

1).  Hannah leans against her locker, but it doesn’t move.

Since Hannah is at rest and there is no displacement so there is no work on Hannah by the contact force

2).  Andy’s car rolls down a hill with the engine off.

Since car is rolled down the hill so here work is done on the car by force of gravity on the car

3). A wind turbine stands still on a sunny, windless day.

Since wind turbine is at rest so there will be no work on the turbine due to force of wind

4).  A balloon expands as it is heated by the Sun.

Here since the volume of balloon is increased so work is done by the internal air of balloon to expand it.

5).  James pedals a stationary exercise cycle that doesn’t move.

While pedaling since the force exerted by the cyclist and the pedal goes down so work is done by the cyclist to move the pedal up and down

true tan speed = ang vel x radius

the area between the graph and the t axis