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Unformatted text preview: The time to travel 60.0 m at a constant speed of 2.00 m/s is 30.0 s. Thus, Pinput = W 2.06 × 10 4 J
=
= 686 W = 0.919 hp .
Δt
30.0 s 4. A 40.0 kg box initially at rest is pushed 5.00 m along a rough, horizontal floor with a constant applied horizontal force of 130 N. If the coefficient of friction between box and floor is 0.300, find (a) the work done by the applied force, (b) the increase in internal energy in the box
floor system due to friction, (c) the work done by the normal force, (d) the work done by the gravitational force, (e) the change in kinetic energy of the box, and (f) the final speed of the box. ∑ Fy = may : n − 392 N = 0 n = 392 N
f k = µk n = ( 0.300) ( 392 N) = 118 N
(a) WF = FΔr cos θ = (130) ( 5.00) cos0° = 650 J (b) ΔEint = fk Δx = (118) ( 5.00) = 588 J (c) Wn = nΔr cos θ = ( 392) ( 5.00) cos90...
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 Fall '08
 CZAJKOWSKI
 Physics, Force, Work

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