# Equivalence principle and Helium balloon.

1. Oct 11, 2008

### KiyoEtAlice

1. The problem statement, all variables and given/known data
Use the equivalence principle to explain the observation that a helium balloon leans forward in a forward-accelerating car.

2. Relevant equations
I don't think equations are needed.

3. The attempt at a solution
I'm completely confused on this question

2. Oct 11, 2008

### D H

Staff Emeritus
While you do not need equations to qualitatively explain this phenomenon, you still need relevant concepts. What are the relevant concepts here?

3. Oct 11, 2008

### KiyoEtAlice

I'm not sure... they only concept that I can think of is the equicalence principle, but I've always been bemused on this subject, so I don't know.

4. Oct 11, 2008

### D H

Staff Emeritus
So, what does the equivalence principle say?

Is this homework, or just a problem that is vexing you? (Be honest.)

5. Oct 11, 2008

### KiyoEtAlice

It's part of the book pratice exercise, nothing complusory, but it's getting on my nerves because it's the last problem of the lot (the other belong to different catorgories).

This is pretty much a straight forward definition: http://www.answers.com/topic/equivalence-principle

Or simple Gravity = acceleration.

Thanks btw

6. Oct 11, 2008

### D H

Staff Emeritus
So, what happens to a balloon in a car suspended in the air from the front bumper? What is the difference between that and the horizontal but accelerating car?

7. Oct 12, 2008

### KiyoEtAlice

Sorry, but I don't get it.

8. Oct 12, 2008

### Rake-MC

He's asking what the difference would be if the balloon were outside or inside of the car.

9. Oct 12, 2008

### KiyoEtAlice

My friend helped explain it to me, so I'm through with this. Thanks anyways.