# Work and Energy

1. Jun 29, 2006

### luis_alonzo

This is my first attempt seeking help on a forum so i hope its in the right place and i did look for similar questions but couldn't find any.

How does energy relate to work?
I have a couple of equations on my book but if you guys could like put here all the equations about energy and work. i know that probably includes a lot. im studying electric charges, planets, and the more common stuff like falling objects and such.
what im looking for is equations that relate kinetic and potencial enrgy to work and how does work relates to the net force of conservative and non conservative forces. i dont know a whole much of physics so if anyone could elaborate a litle on this i would appreciate greatly. i do have a basic understanding of math and calculus but i just dont get the theory involving this subject.

Last edited: Jun 29, 2006
2. Jun 29, 2006

### actionintegral

Hi Luis,

You can learn about energy by starting with the expression x=.5at^2
(The location of an object accelerating uniformly for a time t)

Next multiply both sides of the equation by a. This gives

ax=.5(at)(at) where you know that at=v because the acceleration is
constant.

So ax=.5v^2

Notice that time is not in this equation. That's important.
Also notice that the left side is called "work"
The right side is callled "kinetic energy"

If the acceleration is not constant then you replace ax with adx but

3. Jun 29, 2006

### luis_alonzo

thanks, still if anyone could give me a set of equations that i could use to solve execises. i dont mean to sound lazy because i have looked and its either very complicated to understand or not a big help.
thanks.

4. Jun 29, 2006

### arildno

Exactly what do you find complicated?

5. Jun 29, 2006

### Andrew Mason

$$\text{Energy} = \text{Work}$$

AM

6. Jun 29, 2006

### luis_alonzo

its nothing specific, or rather its a lot of things, but they mostly relate to work. Maybe what im asking for isnt simply stated but i guess i wanted a kind of an underlying theory.

7. Jun 29, 2006

### arildno

And WHAT is the underlying "theory" in Newtonian physis?
What are the basic laws?

8. Jun 29, 2006

### pmb_phy

By the work energy theorem which states that the work done on a particle equals the change in kinetic energy of that particle. The work done on a particles which are acted upon for a conservative force equals the negative change of potential energy. The sum of the potential and kinetic energy for a conservative system is a constant of motion.
See
http://www.geocities.com/physics_world/sr/work_energy.htm

Pete