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Help with this 9th grade motion problem

  1. Jun 4, 2012 #1
    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. jcsd
  3. Jun 4, 2012 #2
    Re: Help with this 9th grade "motion" problem

    Use the conservation of energy to find the relationship between the 2 heights.
     
  4. Jun 4, 2012 #3
    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.
     
  5. Jun 4, 2012 #4
    Re: Help with this 9th grade "motion" problem

    If you throw a stone up with velocity U1, how high does it get?
     
  6. Jun 4, 2012 #5

    HallsofIvy

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    Staff Emeritus
    Science Advisor

    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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