Ch6_GrunfeldM

 **Chapter 6** toc

Work, Energy, and Power


 * Lesson 1: Basic Terminology and Concepts **

=1a: Work =


 * **What is the definition of work?**
 *  **Work** = the act of a force on an object to cause displacement
 * Three key ingredients to work:
 * Force
 * Displacement
 * Cause
 * Everyday __ex:__ a horse pulling a plow through a field, a man pushing a grocery cart down the aisle, etc.
 * The standard metric unit is the Joule ( **J** ), which equals 1 Newton * 1 meter
 * **Negative work** = the act of a force in the opposite direction to hinder motion
 * __Ex:__ a car skidding to a stop on a roadway surface, a baseball runner sliding to a stop, etc.
 * **What mathematics does work involve?**
 * Work can be expressed by the equation:[[image:Screen_shot_2012-01-13_at_9.24.50_AM.png width="150" height="20"]]
 * <span style="font-family: 'Comic Sans MS',cursive;"> **F** is the force, **d** is displacement, and the angle ( **theta** ) is defined as the angle between the force and the displacement vector

=<span style="font-family: 'Comic Sans MS',cursive;">Notes on the Law of Conservation of Energy =




 * <span style="font-family: 'Comic Sans MS',cursive; font-size: 140%;">Lesson 2: The Work-Energy Theorem **

=<span style="font-family: 'Comic Sans MS',cursive;">2a: Internal vs. External Forces =


 * <span style="font-family: 'Comic Sans MS',cursive;">**What is the difference between internal and external forces?**
 * <span style="font-family: 'Comic Sans MS',cursive;">Forces can be categorized based upon whether or not their presence is capable of changing an object's total mechanical energy (KE + PE)
 * <span style="font-family: 'Comic Sans MS',cursive;"> **Mechanical energy** = the energy acquired by the objects upon which work is done
 * <span style="font-family: 'Comic Sans MS',cursive;">External forces:
 * <span style="font-family: 'Comic Sans MS',cursive;">Applied force
 * <span style="font-family: 'Comic Sans MS',cursive;">Normal force
 * <span style="font-family: 'Comic Sans MS',cursive;">Tension force
 * <span style="font-family: 'Comic Sans MS',cursive;">Friction force
 * <span style="font-family: 'Comic Sans MS',cursive;">Air resistance force
 * <span style="font-family: 'Comic Sans MS',cursive;">Internal forces:
 * <span style="font-family: 'Comic Sans MS',cursive;">Gravity forces
 * <span style="font-family: 'Comic Sans MS',cursive;">Magnetic force
 * <span style="font-family: 'Comic Sans MS',cursive;">Electrical force
 * <span style="font-family: 'Comic Sans MS',cursive;">Spring force
 * <span style="font-family: 'Comic Sans MS',cursive;">External forces are referred to as **nonconservative forces** because they are capable of changing the total mechanical energy of an object
 * <span style="font-family: 'Comic Sans MS',cursive;">Internal forces are referred to as **conservative forces** because they are capable of changing the form of energy without changing the total amount of mechanical energy

<span style="font-family: 'Comic Sans MS',cursive;">**Exercises:** <span style="font-family: 'Comic Sans MS',cursive;"> <span style="font-family: 'Comic Sans MS',cursive;">1. PE --> KE because the ball loses height and gains speed <span style="font-family: 'Comic Sans MS',cursive;">2. PE --> KE because the skier loses height and gains speed <span style="font-family: 'Comic Sans MS',cursive;">3. KE --> PE because the baseball is gaining height and losing speed <span style="font-family: 'Comic Sans MS',cursive;">4. KE --> PE because the jumper is losing speed as the bungee cord (spring) stretches <span style="font-family: 'Comic Sans MS',cursive;">5. PE --> KE because the spring is compressed and then starts moving (gaining speed)