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Homework Help: Conservation of Energy

  1. Oct 21, 2013 #1
    1. The problem statement, all variables and given/known data

    A mass m = 2 is in free fall. The acceleration of gravity is g = 10. All numbers are in mks units. The position y(t) and velocity v(t) of the mass as a function of time t are y(t)=9−5t2 and v(t)=−10t. Find each of the energies (K,U,E) as a function of time t. Hint: substitute v(t) into K(v), substitute y(t) into U(y).

    2. Relevant equations

    k = 1/2mv2
    u = mgy

    3. The attempt at a solution

    I know that:
    Work = ΔK
    -ΔU = ΔK

    im having trouble switching the equation to a function of time.
    Am i trying to approach the problem in the wrong way?

    any help is appreciated. Thanks!
    Last edited: Oct 21, 2013
  2. jcsd
  3. Oct 21, 2013 #2
    Your formula for ##U## is a little off. (Hint: check your units!)
  4. Oct 21, 2013 #3
    oh okay i solved the problem thank you!
  5. Oct 21, 2013 #4
    Sure thing, happy to help!
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