As shown in the figure, a block of mass 2.2 kg is pushed up against the vertical
ID: 1460216 • Letter: A
Question
As shown in the figure, a block of mass 2.2 kg is pushed up against the vertical wall by a force of 67 N acting at 53 ? to the ceiling. The coefficient of kinetic friction between the block and the wall is 0.47. The acceleration of gravity is 9.8 m/s 2 .
a) Find the work done by this force in moving the block upward by a distance 1.3 m. Answer in units of J.
b) For a force of F = 67 N, find the magnitude of the frictional force. Answer in units of N.
c) Find the force F needed to keep the block moving up with a constant velocity. Answer in units of N.
Explanation / Answer
work done = force * distance
work done = 67 * 1.3 * sin(53)
work done = 69.561 J
frictional force = k * normal force
frictional force = 0.47 * 67 * cos(53)
frictional force = 18.951 N
for moving the block with constant velocity that means net force will be 0
F * sin(53) = mg + 18.951
F * sin(53) = 2.2 * 9.8 + 18.951
F = 50.725 N
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