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GPE and KE correctness help

  1. Feb 4, 2015 #1
    1. The problem statement, all variables and given/known data
    1) What is the GPE of a 2 kg block 5 meters above the floor?

    2) Joe throws a 4 kg stone straight up and it reaches a height of 5 meters. What is its GPE at its highest point?

    3) How high do you have to lift a 1 kg ball to give it 49 J of GPE?

    4) What is the KE of a 4kg mass at 3 m/s?

    5) What is the mass of an object that has 100J of KE when moving at 5 m/s?

    2. Relevant equations
    Honestly, the only thing I understand is the GPE stuff, which I believe is to simply multiply the mass and height together. I'm not sure if KPE is just as simple.

    3. The attempt at a solution
    1) 10J

    2) I got 20J but it says "highest point" so I don't know if that requires a different formula.

    3) Seems simple enough, I got 49 meters by dividing 49J by 1 kg.

    4 and 5 and basically Kinetic energy in general is what I need help on.
  2. jcsd
  3. Feb 4, 2015 #2


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    Science Advisor
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    Please quote a standard equation for this (answer is wrong).
    Why would the GPE at the highest point follow a different law from the GPE at any other point?
    You haven't been taught any equations for KE?
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