Question

Two blocks of masses m and 2 m placed one over the other as shown in figure. The coefficient of friction between m and 2m is µ and between 2m and ground is µ/3. If a horizontal force F is applied on upper block and T is tension developed in string then choose the incorrect alternative.

• A. If F = $\frac { \mu } { 3 }$ mg , T = 0
• B. If F = µ mg, T = 0
• C. If F = 2µmg, T = $\frac { \mu \mathrm { mg } } { 3 }$
• D. If F = 3µmg, T = 0

Answer 1

Answer: (C)

If F = 2µmg, T = $\frac { \mu \mathrm { mg } } { 3 }$

Answer 2

f_1max = µ mg

f_{2 max} = $\frac { \mu } { 3 }$ (3mg) = µ mg

T= 0 ̃ Tension will be zero in all circumstances