Exercise 5.29 A crate of 38.9 kg tools rests on a horizontal foor You exert a gr

Question

Exercise 5.29 A crate of 38.9 kg tools rests on a horizontal foor You exert a gradually increasing horizontal push on it and observe that the crate just begins to move when your force exceeds 323 N After that you must reduce your push to 201 N to keep it moving at a steady 25.0 cm/s. Part A What is the coefficient of static friction between the crate and the floor? Submit My Answers Give Up Part B What is the coefficient of kinetic friction between the crate and the floor? Submit My Answers Give Up Part C What push must you exert to give it an acceleration of 1.23 m/s2

Explanation / Answer

maximum static friction fs = us*m*g

crate slides when the applied force = maximum static friction fs

F = us*m*g

323 = us*38.9*9.81

coefficient of static friction us = 0.846 <<<<----answer

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part(b)

when the crate moves at steady speed

Fapp = uk = uk*m*g

201 = uk*38.9*9.81

uk = 0.527 <<<====answer

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part(C)

Fnet = F - fk

Fnet = m*a

m*a = F - uk*m*g

F = m*a + uk*m*g

F = (38.9*1.23) + (0.527*38.9*9.81)

F = 249 N <<<<--------answer

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part(D)

F = fs = us*m*g

F = 0.846*38.9*1.62

F = 53.31 N

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part(E)

a = (F - fk)/m

a = (249 - (0.527*38.9*1.62))/38.9

a = 5.55 m/s^2 <<<_------answer

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