Work and Power

formula for work

Force (N) x distance (m) = Work (J)

unit for work and energy

Joules (J)

definition of work

when a force (push or pull) causes an object to move in the direction of the force applied

definition of power

the rate at which work is done (how fast is the work done)

unit for power

Watts (W)

formula for power

Power (W) = Work (J)/time (s)

(Work or not work?)

A waiter carries a tray full of meals above his head by one arm straight across the room at constant speed.

NOT work - force applied to the tray is UP but movement direction is forward

(Work or not work?)

A teacher applies a huge force pushing a wall and becomes exhausted after 15 minutes.

NOT work - wall did not move, so no work done on the wall

(Work or not work?)

A student pushes a stack of chairs down the hallway.

Work IS done - force applied to the chairs and they move in the direction of the force

What TWO things will increase the amount of power?

Doing more work in a given amount of time. OR

Doing the same amount of work in less time.