FrictionHard
Question
Given mA = 30 kg, mB = 10 kg, mC = 20 kg. Between A and B friction coefficient m1 = 0.3, between B and C driction coefficient μ2 = 0.2 and between C and ground μ3 = 0.1. The least horizontal force F to start the motion of any part of the system of three blocks resting upon one another as shown in figure is (g = 10 m/s2)
Options
A.60 N
B.90 N
C.80 N
D.150 N
Solution
(A) Limiting friction between A & B = 90 N
Limiting friction between B & C = 80 N
Limiting friction between C & ground = 60 N
Since limiting friction is least between C and ground, slipping will occur at first between C and ground. This will occur when F = 60 N.
Limiting friction between B & C = 80 N
Limiting friction between C & ground = 60 N
Since limiting friction is least between C and ground, slipping will occur at first between C and ground. This will occur when F = 60 N.
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