HW4-phy2048-Spring-2014-solution

The total work is the sum of the work done by gravity

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Unformatted text preview: a significant amount of deceleration during the 0 ≤ x ≤ 9 interval; nonetheless, its velocity vector still points in the +x direction. 7P42. We solve the problem using the work- kinetic energy theorem, which states that the change in kinetic energy is equal to the work done by the applied force, Δ K = W . In our problem, the work done is W = Fd , where F is the tension in the cord and d is the length of the cord pulled as the cart slides from x1 to x2. From the figure, we have 2 d = x12 + h 2 − x2 + h 2 = (3.00 m) 2 + (1.20 m) 2 − (1.00 m) 2 + (1.20 m) 2 = 3.23 m − 1.56 m = 1.67 m which yields Δ K = Fd = (25.0 N)(1.67 m) = 41.7 J. 7P44. 4 PHY2048 Spring 2014 HW4 (a) Since constant speed implies ΔK = 0, we require Wa = −Wg , by Eq. 7- 15...
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