Work • Work is the transfer of energy through motion • Is work being done on the trays?

Work • Work is only done: – When a force produces motion – A force is exerted through a distance (same direction)

Work

Formula • Work = Force x Distance • W = Fd F= W/d d= W/F

Units • The unit of measurement is the Joule (J) • 1 J = 1 Newton-meter

A Cheesy Video • http: //www. youtube. com/watch? v=b. Nu. Mhnh N 2 -A

Practice Problem • A student’s backpack weighs 30 N. She lifts it from the floor to a shelf 1. 5 m high. How much work is done on the backpack?

Practice Problems • A carpenter lifts a 45 kg beam 1. 2 meters. How much work is done on the beam?

Practice Problems • A dancer lifts a 400 N ballerina overhead a distance of 1. 4 meters and holds her for several seconds. – How much work is done during the lift? – How much work is done while holding her?

Practice Problems • Bricks have a mass of 2. 0 kg. How much work would you do if you lifted 50 of these bricks, one at a time, from the ground to the back of a pick-up truck 85 cm above the ground?

Practice Problems • When you throw a frisbee you might apply about 15 N of force and your hand might cover a distance of 75 cm. How much work would you do if the frisbee’s mass was 141 g?