1. Energy

2. “Something” that enables an object to do work. When you have “Energy” you can do work The amount of energy that an object posses is related to the amount of work the object can do. SI unit is Joules (J) – (N*m) Comes in various forms like ……..

3. Chemical bonds atoms and ions together. Electromagnetic - Electrical moving electric charges. Electromagnetic - Light Energy in the form of light Mechanical associated with motion. Heat/Thermal internal motion of particles. Nuclear in the atomic nucleus. Nuclear fission & Nuclear fusion Five main forms of energy:

4. Mechanical Energy Energy due to the position, or movement, of something Mass is, or will be, displaced (moved) Kinetic or Potential Non-Mechanical Mass is not displaced, no movement or velocity gained or lost Examples Chemical Energy Gasoline Food

5. Potential Energy Energy an object has due to position Stored Energy Stored Work Examples Why do we not walk under ladders Scared of Rubber Bands Gravitational Potential Energy due to gravity acting on an object, PE = mgh PE = mass x gravity x height Metric unit of energy is Joules (same as for work).

6. Sample Problem What is the potential energy of a 6kg bowling ball at a height of 20 meters? Gravitational Potential energy is PE = (mass) x (Gravity) x ( Height ) = (6 kg)x (10m/s/s ) x ( 20 m ) = 1200 Joules What is potential energy on the ground? At a h = 0 m, PE is zero Joules. 20 m 6 kg

7. Kinetic Energy (KE) A stationary object has zero kinetic energy KE = ½ms 2 KE= ½ x Mass x Speed 2 Notice that speed is squared, If speed is doubled what happens to the KE? Energy associated with an object due to its motion. If something is in motion it has the ability to do work Examples How do you stop something that is moving

8. Sample Problem What is the kinetic energy of a 6kg bowling ball, falling from a height of 20 meters with a speed of 20 m/s, just as it reaches the ground? v= 20m/s Kinetic energy is (Kinetic Energy) = ½ ( Mass ) x ( Speed ) x (Speed) = ½ x( 6 kg ) x ( 20 m/s ) x ( 20 m/s ) = 1200 Joules 20 m 6 kg 20 m/s

9. Conservation of Energy Law of Conservation of Energy states that energy can never be created or destroyed. It can only be transformed from one form into another. Example A book falls from a table Draw out and label in Notebook The total Mechanical Energy must always be equal to the sum of Kinetic Energy and Potential Energy E total = KE + PE

10. Pendulum “Like a child on a swing” Energy exchange from PE to KE and back. Maximum Height Maximum Height, again Maximum Speed Can predict speed from height since PE+KE constant Check it out!

11. More than Meets the Eye Watch below as the KE and the PE change as the car changes height and speed. Notice that no matter when you look at the two bars, there is only the same amount of energy that you started with. Watch This!

12. Check for Knowledge Suppose you have a 1 kg mass at a height of 1.25 m. How much potential energy does it have? The mass is now let go. At the very bottom, what is it’s kinetic energy? What is the speed of the mass just before it hits the ground?