Two blocks are connected by a very light string passing over a massless and fric

Question

Two blocks are connected by a very light string passing over a massless and frictionless pulley (see figure). Traveling at constant speed, the 19.5-N block moves 81.0 cm to the right and the 11.6-N block moves 81.0 cm downward. (Let w_1 = 19.5 N and w_2 = 11.6 N.) (a) During this process, how much work is done on the 11.6-N block by gravity? J During this process, how much work is done on the 11.6-N block by the tension in the string? J (b) During this process, how much work is done on the 19.5-N block by gravity? During this process, how much work is done on the 19.5-N block by the tension in the string? J During this process, how much work is done on the 19.5-N block by friction? J During this process, how much work is done on the 19.5-N block by the normal force? J (c) Find the total work done on the 11.6 N block. J Find the total work done on the 19.5 N block. J

Explanation / Answer

(a) Workdone by gravity = m g h

= 11.6 x 0.81

= 9.40 J

a = 0 , T - w2 = 0

T = w2 = 11.6 N

W = (11.6) (0.81) (cos180) = - 9.40 J

(b) W = (19.5)(0.81) (cos90) = 0

by tension, (T = 11.6 N)

W = 11.6 x 0.81 = 9.40 J ....work done by tension.

by fricton.

a = 0 so T - f = 0

f = 11.6 N

W = 11.6 x 0.81 x cos180 = - 9.40 J

By normal force.

W = w1 x 0.81 x cos90 = 0

(c) total work done on both block = 0

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