2. Chapter 6 Work, Energy, Power

3. Work  The work done by force is defined as the product of that force times the parallel distance over which it acts.  The unit of work is the newton- meter, called a joule (J)  Work is a scalar

4. Work  s cos 

5. Work  F cos 

6. Energy  Types of Energy Kinetic Energy = “Motion Energy” Potential Energy = “Stored Energy”

7. Kinetic Energy  Kinetic Energy is the energy possessed by an object because it is in motion.

8. Gravitational Potential Energy  Gravitational Potential Energy is the energy possessed by an object because of a gravitational interaction.

9. Properties of Gravitational Potential Energy  Arbitrary Zero Point  You need to select a zero level  Independent of Path  All that matters is the vertical height change

10. Conservation of Mechanical Energy  Energy can neither be created nor destroyed, but only transformed from one kind to another. Works for systems with no losses (friction, air resistance, etc.)

11. Work Energy Theorem  The amount of kinetic energy transferred to the object is equal to the work done.  KE = W  Many of the problems can be worked from here

12. Problem Solution Guidelines  Determine that energy can be conserved (no losses)  Pick the zero level for potential energy  Pick two interesting places in the problem  Write kinetic and potential energies at these places  Conserve energy (KE + PE) 1 = (KE + PE) 2

13. Power  Power is the time rate of doing work.

14. Power  The unit of power is a joule per second, called a Watt (W).

15. On to problems...