2. Energy ENERGY

3. Energy Defined Energy is the ability of an object to produce a change in itself or the environment.

4. Energy Transfer Work is done when energy is transferred from one form of energy to another.

5. The Units for Measuring Energy Are the same as the units for measuring WORK JOULEs in the SI system FOOT-POUNDS in the British System

6. TYPES OF ENERGY

8. Mechanical Energy Energy is the ability to do work

9. Mechanical Energy(ME) - enables an object to do work A. Kinetic Energy (E k ) - energy of motion B. Potential Energy(E p ) - stored energy

10. Gravitational Potential Energy An object lifted against the force of gravity has stored energy. UNIT= JOULE

11. Gravitational Potential Energy Only changes in potential energy can be measured E p = mgh m= massg= gravityh= height

12. As an object, such as a boulder, begins to move, it gains velocity. Gaining velocity increases the object’s kinetic energy.

13. Example Problem Legend has it that Isaac Newton “discovered” gravity when an apple fell from a tree and hit him in the head. If a 0.20 kg apple fell 7.0 m before hitting Newton, what was its change in E p during the fall?

14. Kinetic Energy Unit: Joules

16. Kinetic Energy Examples Pitched baseball 150 J (148 g @45 m/s) Football linebacker 4500 J (110 kg @ 9.0 m/s)

17. Example Problem A greyhound at a race track can run at a speed of 16.0 m/s. What is the KE of the 20.0 kg greyhound as it crosses the finish line?

18. Work Work is the transfer of energy from one object to another, or... The change in KINETIC ENERGY!

19. E k and E p are constantly changing.

20. Law of Conservation of Energy Energy cannot be created or destroyed. ENERGY is merely transformed.

22. APPARENT LOSS OF ENERGY FRICTION WASTES ENERGY BY CHANGING USEFUL ENERGY INTO HEAT

23. Total Energy At any point, the total energy of an object E t = E k + E p + HEAT

24. Potential Energy to Kinetic Energy

26. Law of Conservation of Energy

28. ELASTIC POTENTIAL ENERGY

29. Elastic Potential Energy Sling shots Trampolines Rubber bands Rubber balls

30. A Jack in the box has stored energy in a compressed spring.

31. k = force to stretch divided by distance stretched The Elastic Constant

32. ELASTIC POTENTIAL ENERGY E EP = 1/2 kd 2

33. Elastic Potential Energy If a spring of stiffness constant (k) is stretched an amount (d), the elastic potential energy stored in the spring is equal to 1/2 the the spring constant times the square of the distance stretched.

35. An automobile stores chemical energy in the gasoline.

36. Thermal Energy The total energy of vibrating atoms and molecules that make up a substance. Temperature is the average KINETIC ENERGY of a substance.