Work and Power

Work Work is the energy necessary to move an object a distance. Work Not Work

Work(Joules) = Force (Newtons) x distance moved (meters) Work Need to know! Work(Joules) = Force (Newtons) x distance moved (meters) W=Fd

Unit of Work Need to Know Work is measured in newton-meters Joule (J) = 1 Newton-meter

Work-Energy Theorem If no change in energy occurs, then no work is done. Whenever work is done, energy changes.

“Working” out A man benches with a force of 2403 N. The distance from his chest to the Top of the lift is .75 m. Find the work done : W = F x D mg d .5FL .5FL

What is the unit of work? Newton Meter Joule Newton meter 3 and 4

How much work is necessary to lift a 15 kg bowling ball 5m into the air?

Power Need to know Power is the rate at which work is done P = average power P = work/time P = W/t Unit: Watt(w)

Power Example: Bench Press If a person benches a weight of 3000 N over a distance of 0.75 m in 5 seconds, estimate the power in his chest and arms

How much power is required to lift 10 kg box, 5 m in the air in 10 s?

Power Example: Running Stairs A 70 kg student runs up a flight of stairs in 4.0s. The height of the stairs is 4.5 m. Estimate the student’s power output in watts mg y = 4.5