Unit+8+-+Work+and+Energy

=Unit 8 - Work and Energy=

__**Khan Adacemy Videos**__
Introduction to Work and Energy - @http://www.khanacademy.org/science/physics/v/introduction-to-work-and-energy Introduction to Work and Energy 2 - @http://www.khanacademy.org/science/physics/v/work-and-energy--part-2

Physics Representation: W SCALAR quantity Definition: "Any change in energy" - "Delta E" (change in E)
 * What is work?**

Equation: Work = (Force)(Distance) __Units:__ (Newtons)(Meters) = **Joules**

You need to **CHANGE POSITIONS** in order to "do work" (in a Physics sense). IOW: You need to work against a force. Example 1: Push book across table = working against friction Example 2: Lifting/Lowering Pen = working against gravity Example 3: Pushing a frictionless object = **NO WORK**

"Energy cannot be created nor destroyed. It can only change forms."
 * Law of Conservation of Energy** - an all encompassing rule for this unit.

The Sum of Energy **in** __//**=**//__ The Sum of Energy **out**
 * "The Work-Energy Theorem", or "WET Theorem"

Example: A pen has energy while resting on the desk. Mr. Blake lifts the pen. **Mr. Blake put energy into the pen** in order for the pen to rise. **Food put energy into Mr. Blake** so he could lift things. **The Sun puts energy into the food** so it can grow. **Nuclear fusion puts energy into the sun** so it can release energy.

In other words, energy transfers from object to object.

//In books: Potential Energy =// U
 * Potential Energy** (gravitational) = PEg

Equation: PEg = (mg)(h) __Units:__ **Joules**

__Comparison:__ Red Pen on Table. Black Pen in Hand held high.

Which has more energy?

Black Pen has more energy because it has a higher position in our gravitational field.
 * So it all depends on where your ZERO POINT (the ground) is located.**

Look at the comparison again. But this time, the ground is the zero point (not the table). YES! Relative to the ground, the pen has a high position. So it has energy. But it's not moving. So it has POTENTIAL energy.
 * Does the Red Pen have energy?**

Equation: KE = (1/2)(mass)(velocity-squared) KE=1/2mv^2
 * Kinetic Energy**

Units for Spring Constant: Newtons/Meter

PEs=1/2kd^2
 * Elastic, Spring, Potential Energy** = (1/2)(spring constant -- N/m)(d-squared -- distance stretched)


 * Elastic Limit = Maximum amount of force you can put on a spring before it deforms.**

Spring Simulation @http://phet.colorado.edu/sims/mass-spring-lab/mass-spring-lab_en.html

//__**Audio/Visual Resources:**__// San Diego Natural History Museum's GIANT Pendulum: @http://www.youtube.com/watch?v=bvUyvBOxPtg&feature=related

__**VIDEO RECORD OF TODAY'S LECTURE:**__