A block of mass, M = 20.0kg, is pulled up a rough incline (of theta = 30.0 degre

Question

A block of mass, M = 20.0kg, is pulled up a rough incline (of theta = 30.0 degree) at a constant speed by a rope that makes an angle of theta = 30.0 degree with the incline. If the tension in the rope is T = 250N and the coefficient of kinetic friction is mu = 0.200, determine the net work done (by all forces) on the process of pulling it (L = 10.0m) up the incline, that is, find: a) W_T, for Tension; b) W_g, for Gravity; c) W_f_K, for Kinetic Friction; and d) W_N, for Normal Force. A car of mass, m = 1550kg, can reach a speed of 60mph (26.8m/s) in Delta t = 7.1 J. What is the average power needed to accomplish that?

Explanation / Answer

1) The first thing you should remember is totalwork done by all forces = Change in K.E from work energy theorem. So work done = Zero since it moves with constant velocity.

Computing individually,

Work ( Tension) = 250* (10) * cos(30)

Work by gravity = 20* 9.8* 10* cos(90+30) =  20* 9.8* 10* cos(90+30)

Work by friction = 0.2* (Normal Force = 20* 9.8*cos(30) ) * 10 * cos(180)

Work done by normal force = N * S * cos(90) = 0

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