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Physics - Work, energy and power

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  • bonkysleuth
    bonkysleuth's Avatar
    267 posts since Mar '07
    • 09 Jul `08, 11:27PM

      When a stone drops to the ground from a height of 5 m, its gravitational potential energy decreases by 10 J. What is the mass of the stone?

       

      Tried to calculate the g.p.e at the top part, which is m X 10ms-2 X 5. but i don't have any idea how to go about doing the next step. By using principle of conservation of energy?

  • wishboy
    wishboy's Avatar
    1,178 posts since Aug '05
    • 10 Jul `08, 1:02AM

      Loss in GPE = mgh

      then sub in those values given to find m

      correct mi if im wrong ><

       

  • Uncertain
    Uncertain's Avatar
    991 posts since Jan '07
    • 10 Jul `08, 9:32AM

      Δmgh = mgΔh (as only the height changes)

       

      Δ in Energy = 10J

       

      10 = mgΔh

       

      Calculate the ‘m’ yourself

       

      PS: I just provide more explanation to wishboy answer.

  • Moderator
    eagle
    eagle's Avatar
    16,326 posts since Aug '01
    • 10 Jul `08, 9:34AM

      Even more info to above

      By using principle of conservation of energy?

      No, you will not be using any conservation of energy at all. Conservation of energy is invoked only when your equation is something like

      total initial energy = total final energy

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