# Help with this 9th grade motion problem

johsun123
Help with this 9th grade "motion" problem

## Homework Statement

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

## Homework Equations

S=u+at u being initial velocity

## 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:

azizlwl

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

johsun123

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.

Villyer

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

Homework Helper

## Homework Statement

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

## Homework Equations

S=u+at u being initial velocity
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?

## The Attempt at a Solution

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