## Friday, March 3, 2017

### Forces in Motion Lesson 2.2 - Work and Power

Work and power are not the same thing in Science even though we sometimes use them interchangeably in speech. Work is when a force moves an object. Forces are often being applied to objects but if there is no movement because of the force, then no work is done. The amount of force and distance determine the amount of work. So

Force x Distance = Work

Work is measured in joules (j).

Power is the rate at which work is done. Walking up a hill and running up a hill create the same amount of work. However, more power is needed to run up the hill.

Work/Time = Power

Power is measured in watts (w).

Questions:
1) If you push on a wall, did you do any work? Why or why not?
2) Compare the amount of work and power needed if you walk up three flights of stairs or run up three flights of stairs.
3) Let's say you applied a force of 300 newtons while you push your bicycle 300 meters. How much work is done? Solve using the equation.
4) Let's say it took you 20 seconds to push the bicycle 90 meters. How much power was needed? Solve using the equation.
5) Riding the bicycle requires only 20 newtons of force to go 90 meters. It takes just 6 seconds. How much work is done? How much power is needed?