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A block weighing 200 N is pushed along a surface. If it takes 80 N to get the block moving and 40 N to keep the block moving at a constant velocity, what are the coefficients of friction μs and μk?
asked Jun 9 in Physics by askzimstudent (5,930 points)

1 Answer

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Best answer
The normal force N is always perpendicular to the surface. The normal force is not always ‘up’. Also, frictional force works opposite in direction to the motion of the block.

For the coefficient of static friction, we need the force needed to get the block moving. In this case, 80 N.

Ff = μsN
N is equal to the weight of the block, so N = 200 N. Substitute-
80 N = μs
·200 N
or
μs = 0.4

For the coefficient of kinetic friction, the force needed to maintain a constant velocity was 40 N. Use the formula:
Ff = μkN
40 N = μk
·200 N
μk = 0.2

The two coefficients of friction for this system are μs = 0.4 and μk = 0.2.e
answered Jun 9 by mr-lee (7,940 points)
selected Jun 9 by askzimstudent
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