1. A 90Kg man is walking up a 45° inclined wooden ramp dragging a 100 KG, 2x2x2

Question

1.      A 90Kg man is walking up a 45° inclined wooden ramp dragging a 100 KG, 2x2x2 meter cubic wooden crate, behind him by means of a rope slung over his shoulder. The rope is attached to center of the front face of crate. The man is 1.6 meters tall at the shoulder. The coefficient of wood on wood static friction is 0.38 and kinetic friction is 0.2 between the ramp and the crate.

Please show me step by step for the 2 questions below

If the man is moving 0.81 m/s what is the coefficient of static friction between his shoes and the board?

If he stops moving will the box slide back down the ramp?

Explanation / Answer

1) coefficient of static friction = (90 * 9.8 * sin45 + 0.2 * 90 * 9.8 * cos45 )/(100 * 9.8)

                                                = 0.763

2)    Here, the box will slide back down the ramp . Because gravitational force is greater than the static force of friction .

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