Published on: Mon Mar 15 2010

Poential Energy is represented by the symbol U.U = mgh WWhat is important is the change in potential energy._{by Gravity}= -ΔU ΔU = U_{Final}– U_{Initial}= 0 – mgh = -mgh ΔU = -mgh = W_{by Gravity}= ΔKE

-ΔU = (U_{Final}– U_{Initial}) = W_{done by Gravity}= ΔKE = KE_{Final}– KE_{Initial}

KETotal Mechanical Energy is Conserved Conservative Force Field: Total work done about a closed path sums to ZERO. Friction Force is non-conservative (You do not get energy back in a closed path) Imagine how force looks as a ball is dropped from the sky. think of_{Final}+ U_{Final}= KE_{initial}+ U_{Initial}

ΔU = -W = -F dU = -dW = -FRead this “The potential Energy with respect to height is equal to mass times gravity times height. Now what about stretched springs? This story is a little different. The force exerted to do work grows as the spring stretch’s further. If you draw a graph, the potential energy of the spring as it is compressed and stretched would form a parabola. Now what about a child on a slide? The component of gravity parallel to the slide is mg cos θ. It is doing work. θ is changing all the time, as the mass of the child moves along the slide._{y }dydU/dy = -F_{y U(y)=mgy }