# notes8 - Potential Energy and Conservation of Energy Work...

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Potential Energy and Conservation of Energy Work Done by Gravity If one lifts an object of mass m from the floor (y i =0) to a height y f =h, you have done work on the object We have imparted energy to it, but it is at rest (v=0). So, this energy is not kinetic energy. It is called Potential Energy (PE or U), or in this particular case, gravitational potential energy U is energy that is stored and which can be converted to another kind of energy, K for example W = F cos φ Δ y = mg ( y f y i ) = mgh

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U g = mgy U is a scalar with units of J in S.I. h is the height above some reference point, e.g. table, floor, … Conservation of (Mechanical) Energy Total (mechanical) energy is constant within some specified system - total energy is conserved - conservation principles are very important in physics; we will see many others later
E is always constant, but K and U can change If U and K change, they must change in such a way as to keep E constant Example Consider the 1D free-fall of an object of mass m

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## This note was uploaded on 12/10/2011 for the course PHY 1111 taught by Professor Stencil during the Fall '11 term at University of Georgia Athens.

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notes8 - Potential Energy and Conservation of Energy Work...

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