Posted by NHS on .
A 8.70kg box is sliding across the horizontal floor of an elevator. The coefficient of kinetic friction between the box and the floor is 0.400. Determine the kinetic frictional force that acts on the box when the elevator is
(a) stationary,
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(b) accelerating upward with an acceleration whose magnitude is 1.00 m/s2, and
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(c) accelerating downward with an acceleration whose magnitude is 1.00 m/s2.
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Physics 
drwls,
a) There is no kinetic friction if the box is stationary (not sliding)
b) and c) Calculate the force applied to the floor. It will be greater than the weight when accelrating upand less than the weight when acclerating down. Multiply that force by 0.400 for the answers.