A block of mass m = 364 g is dragged with a string across a rough horizontal tab

Question

A block of mass m = 364 g is dragged with a string across a rough horizontal table. The string tension is T = 3.27 N, and it pulls upward at an angle of ? = 44.0° with the horizontal. At one particular instant the block is moving at a speed of v = 6.70 m/s. The coefficient of kinetic friction between the block and the table is ?k = 0.639. What is the power supplied to the block by the string tension? What is the power supplied by the force of friction? At this instant the block's speed is (decreasing, constant, increasing or impossible to determine)

Explanation / Answer

Solution:-

A) Using the formula

P = F v cos theta = 3.27 *6.7*cos(44)

=15.76 W

B) Now we have to find friction

N - mg + F sin theta = 0

N = .364*9.81 - 3.27*sin(44)=1.299

Therefore; P friction = -0.639*1.299*6.7

=-6.56 W

At this point block, speed is decreasing

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