Section 1: Work and Power What is work? Which picture shows work being done? The one where kids are having fun playing basketball or the one where a girl appears to be working hard on her school work?

Section 1: Work and Power What is work? In physics, work means the use of force to move an object. The teens who are playing basketball in the picture are using force to move their bodies and the basketball, so they are doing work. The teen who is studying isn’t moving anything, so she isn’t doing work.

Section 1: Work and Power Work is done when a force causes an object to move in the same direction that the force is applied. For work to be done, the force must be applied in the same direction that the object moves. If a force is applied in a different direction than the object moves, no work is done. (Refer to figure 2 on pg. 407)

Section 1: Work and Power (pg. 407) Force in Two Directions When you exert force at an angle, only part of your force does work; the part that is in the same direction as the motion of the object. (see lawnmower example- pg. 407)

Section 1: Work and Power (pg. 408) Calculating Work Work Equation work (in joules) = force (in newtons) x distance (in meters) W= Fd Work cartoon

Section 1: Work and Power (pg. 407) Calculating Work Work Equation W= Fd Practice: As you push a lawn mower, the horizontal force is 300 N. If you push the mower a distance of 500 m, how much work do you do? 300 x 500 = 150,000 J

Section 1: Work and Power (pg. 409) What is power? Power is the measure of the amount of work that can be done in a given amount of time, or how quickly work is done.

Section 1: Work and Power (pg. 409) Calculating Power Power Equation power (in watts) = work (in joules) time (in seconds) P = W t Golf- work and power Practice Question: You do 140 J of work in 20 s. How much power do you use? 140/20 = 7 watts

Section 1: Work and Power (pg. 410) Work and Energy If you push on an object and make it move, you do work on the object and change its energy. Energy of motion = kinetic energy If you lift an object higher above Earth’s surface, you do work on the object and change its energy. Increase in height= increase potential energy