Question

Two blocks A and B each of mass m are placed on a smooth horizontal surface. Two horizontal forces F and 2F are applied on blocks A and B, respectively, as shown in $Fig.$. Block a does not slide on block B. Then the normal reaction acting between the two blocks in (assume no friction between the blocks)

• A. $F$
• B. $f/2$
• C. $\frac{F}{\sqrt{3}}$
• D. $3F$

Answer 1

The correct option is D $3F$

Consider Both masses as a system,

Total force on system $F_T=2F-F=F$ (Left side)

Mass of system $M=2m$

Acceleration of two mass system is $a=\frac{F}{2m}$ towards left free body diagram is

$N\cos 60-F=ma$

$N\cos 60-F=\frac{F}{2}$ $[a=\frac{F}{2m}]$

$\frac{N}{2}=\frac{3F}{2}$

$N=3F$

Normal reaction acting between two blocks $=N=3F$

Hence,

option $\left(D\right)$ is correct answer.