# Help with this 9th grade motion problem

1. Jun 4, 2012

### johsun123

Help with this 9th grade "motion" problem

1. The problem statement, all variables and given/known data

2 stones are thrown vertically upwards with initial velocities U1 & U2. Prove that heights recahed by them is in ration U1squared:U2squared.

2. Relevant equations

S=u+at u being initial velocity

3. The attempt at a solution

since a and t will cancel out, ration should be u1: u2 not the squared. What am I missing?

Last edited: Jun 4, 2012
2. Jun 4, 2012

### azizlwl

Re: Help with this 9th grade "motion" problem

Use the conservation of energy to find the relationship between the 2 heights.

3. Jun 4, 2012

### johsun123

Re: Help with this 9th grade "motion" problem

Care to explain it a bit more? Which is the equation you are referring to?

We are yet to learn law of conservation of energy.

4. Jun 4, 2012

### Villyer

Re: Help with this 9th grade "motion" problem

If you throw a stone up with velocity U1, how high does it get?

5. Jun 4, 2012

### HallsofIvy

Staff Emeritus
Re: Help with this 9th grade "motion" problem

This is incorrect. u+ at is the formula for the speed at t seconds given initial velocity u and acceleration t. Do you have a formula for distance or height of an object moving with constant acceleration?

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