While working your summer job at the FedEx office moving crates, you get tired o
ID: 2236870 • Letter: W
Question
While working your summer job at the FedEx office moving crates, you get tired of lifting heavy boxes all day. Too much work. So you decide to calculate the work done by friction on a box that slides down a 150 cm long ramp as shown. You estimate the box to be m=5 kg. The coefficient of kinetic friction is ?k=0.31. Find a) the work done by friction, b) the work done by gravity, c) the workdone by the normal force, d) the total work done on the box. e) if the box has a speed of 2.2 m/s(downward) at the top of the ramp what is its speed at the bottom?Explanation / Answer
F(friction) = k*N = 0.31 * 5 * 9.8 = 15.19 N
A) work done(friction) = force * distance = 15.19 * (-150/100) = 22.785 J (distance in opp. dir.)
B) work done(gravity) = force * distance = 9.8 *5 * (150/100) = 73.5 J ( bcoz distance in the direction of force is =0 )
C) B) work done(normal) = force * distance = 9.8 *5 * (0) = 0 J ( bcoz distance in the direction of normal force is =0 )
D) Total work = 22.785 + 73.5 = 96.285
E) v^2 = U^2 + 2as = (2.2)^2+(2*9.8(1-k)*1.50) =
v= 5 m/s
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