A small block with a mass of 0.0600 kg is attached to a cord passing through a h

Question

A small block with a mass of 0.0600 kg is attached to a cord passing through a hole in a frictionless, horizontal surface (Figure 1) . The block is originally revolving at a distance of 0.49 m from the hole with a speed of 0.63 m/s . The cord is then pulled from below, shortening the radius of the circle in which the block revolves to 0.17 m . At this new distance, the speed of the block is 1.82 m/s.

A) What is the tension in the cord in the original situation when the block has speed v0 = 0.63 m/s ?

B) What is the tension in the cord in the final situation when the block has speed v1 = 1.82 m/s ?

C) How much work was done by the person who pulled on the cord?

Explanation / Answer

A) ByT = mv^2/r = [0.0600 x (0.63)^2]/0.49 = 0.0486 N
B) By T = mv^2/r = [0.0600 x (1.82)^2]/0.17 = 1.169 N
C) By work energy relation:-
=>W = KE
=>W = 1/2mv^2 -1/2mu^2
=>W = 1/2 x 0.0600 x [(1.82)^2 - (0.63)^2]
=>W = 0.087 J

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