1. Hasn’t it ALL been work so far? Mr. Fox’s 8 th Grade Science Class.

2. What is Work? Work – force exerted on an object causing it to move. IN order for you to do work The object must move some distance as a result of your force The force you exert must be in the same direction as the object’s motion.

3. Calculating Work Work = Force x Distance Units: N·m or J joule – (J) is the amount of work you do when you exert 1 newton of force, 1 meter.

4. Practice Problems (1) A hydraulic lift raises a 12,000N car 2 meters. How much work is done on the car? You exert a force of 0.2N to lift a pencil off the floor. How much work do you do if you lift it 1.5m?

5. Practice problems (2) If the car that is 12,000 N has a mass of 1224.489kg. What is the acceleration on the car? You do 1300 J of work moving a 100N object. How far was the object moved? You did 4000J of work moving an object 45m. How much force did you need to exert to move it?

6. Pressure Pressure – is equal to the force exerted on a surface divided by the total area over which the force is exerted. Pressure = Force / Area Unit = N/m 2

7. When do we use Pressure Measurements? Air Pressure – weather, tires, etc. Water Pressure – how much water an object can hold, how deep a submarine can go.

8. Practice Problems 1. We fill a tire has 35 square inches of area, and the air exerts a force of 3500N. What is the pressure being exerted by the air? 2. A tire has an air pressure of 40 pounds per square inch. If the force exerted by the air is 20,000N, what is the area of the tire?

9. Power The rate at which work is completed. Power = work ÷ time The unit is either J/s or a W (which is a watt)

10. Practice Problems 1. Gareth is lifting the motor out of his car using a pulley system. The pulley system used 5000N of force to life the engine 1.342m into the air. It takes him about 900s to do this. How much work did the pulley do? How much power did it have? 2. Mr. Fox used 4986J of work to get down the hallway in 4.79s. How much power did he generate?