1. Work and Power Chapter 13.1 Notes

2. What is work? Work is done only when force is applied to an object AND the object moves in the same direction as the applied force Work is calculated by multiplying the force by the distance over which the force is applied work = force x distance W = Fd

3. When is work done? Work is zero if an object does not move Even though this weightlifter is applying a lot of force to the barbell as she holds it over her head, is she doing any work?

4. SI Unit for Work To find work, we calculate force (measured in newtons) times distance (measured in meters) The SI unit for work is called the joule (J) 1 joule is equal to one kilogram times meter squared per second squared 1 N x m = 1 J = 1 kg x m 2 /s 2

5. What is power? Power measures work in relation to time Power is the rate at which work is done, or how much work is done in a given amount of time power = work/time P = W/t

6. SI Unit for Power The SI unit used to express power is the watt (W) One watt is the amount of power needed to do one joule of work in one second Do not confuse the symbol for work, W, which we italicize, with the symbol for the watt, W