Three blocks of A, B and C of equal mass m are placed one over the other on a smooth horizontal ground as shown in figure. Cofficient of friction between any two blocks of A,B and C is 1/2. The maximum value of mass of block D so that the blocks A,B and C move without slipping over each other is-

Options

A. 6 m
B. 5 m
C. 3 m
D. 4 m

Answer

3

Explanation

Block B & C move together but
For A `malemu(mg)`
So `a_(max)=mu_(s)g`
So `a_(max)=(Mg)/(M+3m)`
M=3m