1. Work, Power and Energy

2. WORK Is the product of force and distance Work is done when a force acts on an object in the direction the object moves. No movement, no work is done

3. Work Formula Work = Force x distance W= F x d Unit for Work= joule (J)

4. Work Practice 1. A man weighing 750 N climbs a flight of stairs 5 m high. How much work has he done?

5. 2. A 10 N book is raised 500 meters from the floor. How much work is done?

6. 3. Kayla does 40 J of work while pushing a shopping cart 30 meters. What is the force applied?

7. 4. David pulls a 450 N sofa up the stairs producing 25 J of work. How far did he pull the sofa?

8. 5. A 100 kg object is pulled vertically upward 5.0 m by a rope with an acceleration of 1.0 m/s 2. Find the work done by the tension force in the rope.

9. Rate of doing work Doing work at a faster rate requires more power. To increase power, you can increase the amount of work done in a given time.

10. Formula: Power= Work/time (s) P = W/t Unit: J/s or Watt (W)

11. Power Practice 1. A motorcycle does 2000 J of work in 25 seconds. How much power is produced?

12. 2. Sean does 125 J of work in 50 seconds. How much power is produced?

13. 3. Kayla produced 20 W of power in 0.5 seconds. How much work was done?

14. 4. Jacob does 400 J of work to produce 15 W of power. How long did he work?

15. 5.Beth moves a 15 N book 20 meters in 10 seconds. How much power was produced?

16. Machines Machine — a device that changes a force Machines make work easier to do Types of simple machines Inclined Plane Wedge Screw Wheel and Axle Lever Pulley

17. S IMPLE MACHINES INTERACTIVE http://www.beaconlearningcenter.com/weblessons /simplemachines/machines001.htm http://app.discoveryeducation.com/player/?assetG uid=c0b82efb-9df0-42e1-ac6b- da0b470474b2&fromMyDe=0&isPrinterFriendly =0&provider=&isLessonFromHealth=0&productc ode=US&isAssigned=false&includeHeader=YES &homeworkGuid= Compound machine- two or more simple machines that operate together

18. E NERG Y The ability to do work. Measured in Joules (J) Two major types Kinetic Potential

19. Kinetic Energy The energy of motion The kinetic energy of any moving object depends upon its mass and speed Measured in Joules (J) Formula: KE = ½ mv 2

20. Kinetic Energy Practice 1. A 3 kg ball is rolling 2 m/s. How much kinetic energy does it have?

21. 2. Determine the kinetic energy of a 625-kg roller coaster car that is moving with a speed of 18 m/s.

22. 3. A 30-kg car is going down a hill with a speed of 5 m/s. What is the cars kinetic energy?

23. Potential Energy Is the energy that is stored as a result of position or shape Two types Gravitational PE – depends on height Elastic PE – objects stretched or compressed - shape

24. GPE - depends on its mass, its height, and the acceleration due to gravity Formula: GPE = mgh m=mass g= acceleration due to gravity (9.8 m/s/s) h=height Unit: Joule

25. Potential Energy Practice 1. A 4 kg rock is sitting on a 3 m ledge. How much potential energy does it have?

26. 2. A 625-kg roller coaster is sitting at the top of the hill 90 meters from the ground. What is the coaster’s potential energy?

27. 3. A book has 40 J of potential energy when it is 5 meters from the ground. What is the book’s mass?

28. F ORMS OF ENERGY Mechanical : energy in motion ex: water falls, car Thermal : internal motion of particles ex: fire Chemical : chemical changes and bonds ex: lighting a match, chemical reactions Nuclear : splitting of atoms ex: sun Electromagnetic : electrical charges ex: spectrum, light waves, electromagnets

29. Energy Conservation Energy cannot be created or destroyed

30. Energy Conversions The gravitational potential energy of an object is converted to the kinetic energy of motion as the object falls P.E. greatest K.E. greatest P.E. greatest conversion

31. P ENDULUMS AND ENERGY 1. P.E. greatest 2. P.E. decreases and K.E. increases 3. K.E. greatest 4. K.E. decreases and P.E. increases 5. P.E. greatest

32. P ROJECTILE M OTION Projectile Motion site When an object has a forward force and gravity affecting its path. How many forces are acting on it? TWO (Forward and gravity) Ex: baseball, bullet from a gun