I was wondering if anyone knows how to calculate joels. and kinetic energy and stuff. I really need help. can any 1 teach me how to do it?

Joules is an unit measured for amount of energy.

 

Two kind of engeries that are commonly known for novices: Kinetic and Potential energy.

 

[math]KE = \frac{1}{2}mv^2[/math]

[math]PE = mg(y_2 - y_1)[/math]

 

Both of them have the answers in the unit of Joules.

 

Any other questions?

yeah, can you give me a problem to solve before the test? i really need help in 30mins thats when i go to school. please help me. I want an example before i go.

Suppose you have a ball that is 5 kg and it have a velocity of 10 m/s, the ball would have 250 Joules of energy.

 

[math]KE=\frac{1}{2}mv^2[/math]

[math]KE=(0.5)(5)(10^2)[/math]

[math]KE=250J[/math]

 

But in real world, that doesn't happen due to air resistance and friction, so it would be slight less than 250 Joules.

well in that case the ball would have 250 joules of translational kinetic energy, the friction and air resistance would only act to slow the ball down.

 

you do have to define what kind of energy your talking about however is what kind of energy it is. Objects have all sorts of energies you an assign to them, for instance there is rotational kinetic energy, chemical energy, potential energy, and most likely a few others that I haven't heard about.

 

its also useful to remember that thats kinetic energy relative to you, if you started moving 2 m/s in the other direction, and looke at the original ball, you would come to the conclusion that it had 360 joules of energy.

Good point CPL.Luke, thanks.