ATAR Notes: Forum

VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Physics => Topic started by: /0 on June 13, 2008, 03:40:07 am

Title: When to use what (energy)
Post by: /0 on June 13, 2008, 03:40:07 am
I've got two questions that they don't ask in the textbook lol

1. Is the kinetic energy in orbit the same as the kinetic energy of any moving object?

i.e. ?

2. Why and when should you use gravitational potential energy as opposed to 'normal' potential energy?

I've heard people say you use when you're close to the ground, but that isn't enough of a reason for me... after all, one is positive and one is negative! A varying gravitational field can't possibly answer a difference that large!

?  ?  ?

Thanks
Title: Re: When to use what (energy)
Post by: Neobeo on June 13, 2008, 07:54:31 am
Assuming I interpreted both questions correctly,

(http://img127.imageshack.us/img127/2373/divzeroqz6.png)

Note that these are both quantitative arguments. I can't give a completely definite answer as to when you should use what type of energy. I'm just laying out the concept behind the different formulas and how they are derived, so that a more conscientious decision can be made.
Title: Re: When to use what (energy)
Post by: /0 on June 13, 2008, 02:59:52 pm
Wow thanks Neobeo! Looks like you put a lot of work into that. I think I understand now how is "absolute" and how is relative.

But I don't get how you came to ?
Title: Re: When to use what (energy)
Post by: Mao on June 13, 2008, 04:51:01 pm
fundamental theorem of calculus:

if is relative to earth:



Title: Re: When to use what (energy)
Post by: Neobeo on June 13, 2008, 05:14:33 pm

Then just take the derivative with respect to R.
Title: Re: When to use what (energy)
Post by: /0 on June 13, 2008, 05:19:10 pm
Ok thanks Mao and Neobeo! ^^