1. Friday PS 11-2 Answers to homework

2. Hand in homework Mousetrap game chart Halloween questions (Simple machine pictures)

3. Mousetrap questions?

4. Answers to Page 390 HW 1)lever, pulley, wheel and axle, inclined plane, wedge, and screw 2)a. screw b. inclined plane c. 1 st class lever 3)Bigger output force exerted over a smaller distance 4)Middle of pulley is fulcrum, outside edge of wheel is like a lever extended into fulcrum. They are different because you can change the position of the fulcrum of a lever

5. HW p390 5) A long, thin wedge has a greater mechanical advantage than a short, wide wedge because of ratio of its length to its height is greater 6) No 7) Greater distance input uses less input force 8) Answer will varying

6. Energy Is the capacity to do work Work is the quantity of energy transferred by force to an object that results in movement of object in direction of force Energy is the currency of physics

7. Energy units Since the amount of work done = the amount of energy transferred… Wherever work is done, energy is transferred or transformed to another system The units for work and energy are the same

8. Energy is like money Different types of money- different forms of energy Supplies the ability to produce a certain type of force or means to store the energy for later use –Action –Storage

9. Mechanical energy The amount of energy available for use or storage by macroscopic physical means Energy related to what you can do with or to an object

10. Mechanical -vs- nonmechanical energy Non-mechanical Energy Energy that lies at the level of atoms and that does not affect the motion on a large scale –Thermal energy –Chemical energy –Nuclear Energy –Electrical Energy

11. Potential energy Stored energy 2 forms of mechanical potential energy –Elastic Potential Energy (EPE) Store by changing shape –Gravitational Potential Energy (GPE) Store by changing location Can calculate GPE as –GPE = mgh g = acceleration due to gravity (9.8 on Earth) h = distance above the reference line

12. Elastic potential energy

13. Kinetic Energy Energy of motion KE = ½mv 2 m = mass v = velocity

14. Problems on energy Class Examples:

15. In Class Assignment Energy Problem Handout Watch for units