42. A 5.0 kg block of steel slides down a ramp with acceleration 0.40 m / s 2 directed down the ramp. The ramp makes an angle of o 37 with the horizontal. What is the coefficient of kinetic friction between the block and the ramp?
(A) 0.50
(B) 0.70
(C) 0.25
(D) 0.75
(E) 5.0

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統計： A(2), B(33), C(3), D(4), E(0) #2020486