1. Energy Notes

2. Energy When you do work on an object you must displace that object from its rest position. When you do work on an object you must displace that object from its rest position. In this case that object then has the ability to do work on some other object (one way is for the original object to collide into it) In this case that object then has the ability to do work on some other object (one way is for the original object to collide into it) We call this ability to do work ENERGY. We call this ability to do work ENERGY.

3. Energy Energy can exist because of the object's motion (Kinetic Energy) Energy can exist because of the object's motion (Kinetic Energy) It can also exist because of its position (Potential Energy). It can also exist because of its position (Potential Energy).

4. Kinetic Energy Kinetic Energy=.5 (mass)(velocity) 2 Kinetic Energy=.5 (mass)(velocity) 2 KE=.5mv 2 KE=.5mv 2 the units on this will be kg m 2 /s 2 or a Joule—J (Nm—newtons x meters) the units on this will be kg m 2 /s 2 or a Joule—J (Nm—newtons x meters) Sample Problem p. 193 Sample Problem p. 193

5. Potential Energy There are different types of potential energy (chemical, elastic, gravitational, & nuclear), but all depend upon the position of the object. There are different types of potential energy (chemical, elastic, gravitational, & nuclear), but all depend upon the position of the object. Gravitational Potential Energy (GPE) is the energy due to an object's position above the Earth. Gravitational Potential Energy (GPE) is the energy due to an object's position above the Earth.

6. Gravitational Potential Energy G.P.E. = (mass) x (acceleration of gravity) x (displacement of the object to the earth)=mgh G.P.E. = (mass) x (acceleration of gravity) x (displacement of the object to the earth)=mgh The units on this would also be a Joule. The units on this would also be a Joule. Sample Problem p. 191 Sample Problem p. 191

7. Elastic Potential Energy Elastic Potential energy is the energy due to the stretching or compression of an elastic material. Elastic Potential energy is the energy due to the stretching or compression of an elastic material. E. P. E. =.5 x (elasticity constant) x (amount of displacement from equilibrium) 2 =.5 k Δx 2 E. P. E. =.5 x (elasticity constant) x (amount of displacement from equilibrium) 2 =.5 k Δx 2 The units for k (elasticity constant) are in N/m The units for k (elasticity constant) are in N/m

8. Non-mechanical Energy If the energy is a macroscopic quantity it is considered to be mechanical energy (most kinetic or potential energy). If the energy is a macroscopic quantity it is considered to be mechanical energy (most kinetic or potential energy). If not, then it is considered non- mechanical. If not, then it is considered non- mechanical. Heat, Sound, Light, and all other electromagnetic radiation are types of non-mechanical energy. (and actually are kinetic) Heat, Sound, Light, and all other electromagnetic radiation are types of non-mechanical energy. (and actually are kinetic)