a block is on a horizontal surface and another one hanging down from it by a pul

Question

a block is on a horizontal surface and another one hanging down from it by a pulley.

A) The pulley and string are massless and there is no friction. if the system is released from rest, what is its speed after the masses have moved a distance b?

B) The pulley and strings are massless. the coefficient of kineti friction between the block and the plane is 0.2, and m= 5 kg

1) how much work is done against friction as the system moves 3m?

2) if it is initially at rest what is its speed after it has moved 3m?

Explanation / Answer

A) ( m + m) v^2 /2 = mgb

v = sqrt(gb)

b)   = 0.2mg x 3 = 29.4 J

c) (m + m)v^2/2 + 29.4 = mg x 3

v   =4.85 m/s

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