Work is the product of the force applied and the distance an object moves in the direction of the applied force. Power is the rate at which work is done, or the amount of work done per unit of time. It is measured in watts. James Watt defined the unit of horsepower based on the power output of a strong draft horse to provide a useful comparison for his steam engines.

1. 14.1 Work and Power When Does a Force Do Work? How Are Work and Power Related?

2. What is Work? Work is the product of force and distance For a force to do work on an object Some force must act in the same direction as the object moves. No movement = No work done Work requires motion

3. Work Depends on Direction Any part of force that does not act in the direction of motion  Does no work on an object Work = Force X Distance Units of work = Joule Derived unit of Newton x Meter (N x m) (Name after James Prescott Joule 1818-1889)

4. What Is Power? Power = is the rate of doing work. Doing work at a faster rate requires more power. Increasing your power increases amount of work done in a given time.

5. Examples of Power Ex. Using a Snow blower compared to shoveling a walkway… Which is faster? The size of engine used by a machine indicates its power.

6. Calculate Power! Calculate Power: Power = Work / Time Units for Power = Watt (W) 40-watt light bulb requires 40 joules each second that it is lit. The same amount of energy is used to raise your book 1 meter high in half a second

7. James Watt and Horsepower Horsepower is another unit of power Horsepower (hp) is = to 746 watts James Watt first defined Watt was looking for a comparison for the steam engines he had invented. Used horse as they were used most in the 1700s

8. James Watt and Horsepower Defined the Horsepower based on the power output of a very strong horse. Ex. If you have a 4hp Rototiller it would get as much work done as a plow pulled by 4 horses.