A 1,500-N crate is being pushed across a level floor at a constant speed by a fo
ID: 1777515 • Letter: A
Question
A 1,500-N crate is being pushed across a level floor at a constant speed by a force F of 310 N at an angle of 20.0° below the horizontal, as shown in the figure a below. 20. 0° 20.0° (a) What is the coefficient of kinetic friction between the crate and the floor? (Enter your answer to at least three decimal places.) (b) If the 310-N force is instead pulling the block at an angle of 20.0° above the horizontal, as shown in the figure b, what will be the acceleration of the crate? Assume that the coefficient of friction is the same as that found in part (a)Explanation / Answer
let coefficient of kinetic friction = uk
Normal force = N
weight of box, W = mg = 1500 N
F = 310 N
let angle = A = 20o
for figure a)
speed is constant => net force = 0
in vertical, N = W + Fsin20o
in horizontal, Fcos20o = ukN
=> 310cos20o = uk(1500 + 310sin20o)
=> uk = 0.18138
in figure b)
vertical, N = W - Fsin20o
Horizontal, Fco20o = ukN + ma
=> 310cos20o = 0.18138 x (1500 - 310sin20o) + (1500/9.8)a
=> a = 0.2513 m/s2
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