PH-UY 1013 Lecture 13: Work and potential energy
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W g =-(mgy f -mgy i ) let u g =mgy w g =-(u gf -u gi )=- u g u g =gravitational potential. 2 ) let u s =0. 5kx 2 > w s =-(u sf -u si )=- u s u s =spring potential energy energy. K m 2 m = n m = j. /mn m2 = n m = j. Not possible to write the work done by tension, normal force, or friction as w=-[f(final pos)-f(initial position)] (general)if u is the potential energy associated with a particular force, then the work done by that force is the negative of the change in potential energy. W=- u kq q1 2 kq q1 2 ri. If work done by non-cons forces is zero then (must be frictionless, object is sliding or swinging) Suppose k=300n/m, and spring is initially compressed by 40cm (no friction) and m=2kg k.