Question

Two blocks A and B each of mass $m$ are placed on a smooth horizontal surface. Two horizontal force $F$ and $2F$ are applied on both the blocks A and B, respectively, as shown in figure. The block A does not slide on block B. Then the normal reaction acting between the two blocks is:

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

Answer 1

The correct option is A $3F$

Given,

Two blocks of equal $mass=m$

Horizontal forces $F,2F$

So, Acceleration of two mass system is $\frac{F}{2m}$ towards left.

So,

$Ncos{60}^0-F=m\times \frac{F}{2m}=\frac{F}{2}$ Since, $cos{60}^0=\frac{1}{2}$

Where N is the normal reaction.

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

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

$N=3F$

Thus the normal reaction acting between ]two blocks is $3F$