The coefficient of static friction between a 40kg crate and concrete surface is 0.25. Find the magnitude of the minimum force needed to keep the crate stationary on the concrete base inclined at 45o to the horizontal. [G = 10ms-1]
-
A.
400N -
B.
300N -
C.
283N -
D.
212N
Correct Answer: Option D
Explanation
momentum force = Rsin(theta) – (mu)Rcos(theta)
Fm = (40 x 10 x sin 45) – (40 x 10 x 0.25 x cos 45)
= 212N