Question
Question: Given m<sub>A</sub> = 20 kg., m<sub>B</sub> = 10 kg, m<sub>C</sub> = 20 kg, between B and C µ<sub>2<...
Given mA = 20 kg., mB = 10 kg, mC = 20 kg, between B and C µ2 = 0.3 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) –
A
60 N
B
90 N
C
80 N
D
50 N
Answer
50 N
Explanation
Solution
Limiting friction between A and B = 60 N
Limiting friction between B and C = 90 N
Limiting friction between C and ground = 50 N
Since limiting friction is least between C and ground, slipping will occur at first between C and ground. This will occur when F = 50 N