Question

14. A block of mass m is placed on another block of mass M lying on a smooth
horizontal surface. The coefficient of static friction between m and M is Us What is
the maximum force that can be applied to m so that the blocks remain at rest
relative to each other?
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Answer 1

Answer:

Here, the force applied should be such that frictional force Acting on the upper block of m should not be more than the Limiting friction (=μ1mg).

For non-slipping condition

Force in upper block f≤μmg (limiting friction)

ma=μ1mg

a=μ1g.........(1)

Friction force on mass M, is μ2(M+m)g

Let the system moves with Acceleration a . Then for whole system:

F−μ2(M+m)g=(M+m)a.........(2)

From equations (1) and (2), we get

F=(M+m)g(μ1+μ2)

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Answer 2

Explanation:

A block of mass m is placed on another block of mass M, which itself is lying on a horizontal surface. The coefficient of friction between two blocks is u and that between the block of mass M and the horizontal surface is u. What is maximum horizontal force can be applied to the lower block so that the two blocks move without separation?

A

(M+m)(μ2−μ1)g

B

(M−m)(μ2−μ1)g

C

(M−m)(μ2+μ1)g

D

(M+m)(μ2+μ1)g

Correct Answer