2012_1061_Lecture_Ch_078

18 conservation of energy chapter 8 skier starts at

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Unformatted text preview: = lim = ∆t→0 ∆t dt dW P= = dt ￿ ￿ ￿x d F ·￿ dt x ￿ · d￿ = F · ￿ ￿v =F dt Figure 7.18 Conservation of Energy Chapter # 8 Skier starts at the top of the hill  On which run does her gravitational energy change the most (a), (b), (c), (d) or are they all the same? Assume no friction Falling ball of mass m Conservative and Non-Conservative Forces Ball raised along a two dimensional path We call a force conservative if: the work done by the force on an object moving from one point to another depend only on the initial and final positions of the object, and independent of the particular path taken WG = ￿ 2 ￿ Fg · d￿ l 1 = ￿ 2 mg cos θdl 1 WG =− ￿ y2 mgdy y1 = −mg (y2 − y1 ) φ = 180◦ − θ cos θ = − cos φ dy = dl cos φ continued  A force is conservative if the net work done by the force on an object moving around any closed path is zero Potential Energy − → − → Wext = F ext · d = mgh cos 0◦ = mgh = mg (y2 − y1 ) → − →− WG = F G · d = mgh cos 180◦ = − mgh = − mg (y2 − y1 ) ∆U = U2 − U1 = Wext = mg (y2 − y1 ) ∆U = U2 − U1 = ...
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This note was uploaded on 02/03/2014 for the course PHYSICS 1061 taught by Professor Tsankov during the Fall '09 term at Temple.

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