1. Chapter 6 Notes

2. Chapter 6 6.1 Work  Work is equal to the product of the magnitude of the displacement times the component of the force parallel to the displacement (in same direction)  W=Fd or W=Fd cos   Work (joule) = Force (newton) x distance (meters)

3. Chapter 6 6.3 Kinetic Energy  kinetic energy - energy of motion  KE = _ mv 2  W net = KE 2 -KE 1 =  KE  Work-energy principle - The net work done on an object is equal to the change in its kinetic energy

4. Chapter 6 6.4 Potential Energy  potential energy - energy associated with position or configuration  gravitational potential energy - PE =mgy or PE=mgh  Work done by external force: W ext = PE 2 -PE 1 =  PE  Work done by gravity: W G = -  PE

5. Chapter 6 Spring potential energy  Spring force = - spring constant x displacement  Fs = -kx  Diagram pg. 156  Spring Elastic PE = _ kx 2

6. Chapter 6 6.5 Conservative and Non- Conservative forces  Conservative - work done does not depend on the path taken (gravity, elastic, electric)  Non-Conservative - work done depends on the path taken (friction, air resistance, tension)  Potential energy can only be defined for a conservative force.

7. Chapter 6  C-Conservative  NC- Non-conservative  W net = W C + W NC  W C = -  PE  W NC =  KE +  PE

8. Chapter 6 Conservation of Mechanical Energy  W NC = 0 no non-conservative forces present   KE +  PE = 0 for conservative forces only  E = KE + PE  KE 2 + PE 2 = KE 1 + PE 1 for conservative forces only

9. Chapter 6 6.7 Problem solving using conservation of energy  E = KE + PE = _ mv 2 +mgy  When gravity only acts on object: _ mv 2 1 +mgy 1 = _ mv 2 2 +mgy 2  from top to bottom PE 1 =KE 2  Energy bucket pg. 160  Spring energy: _ mv 2 1 + _ kx 2 1 = _ mv 2 2 + _ kx 2 2

10. Chapter 6 6.8 Conservation of Energy  Read pg. 166  The total energy is neither increased nor decreased in any process. Energy can be transformed from one form to another, and transferred from one body to another, but the total amount remains constant.

11. Chapter 6 6.10 Power  Power is the rate at which work is done  Power = work/time = energy transformed/time  Power (watts) = work (joules)/ time (sec)