Question

In the arrangement shown in figure, coefficient of friction between the two blocks is $\mu =\frac{1}{2}$. The force of friction acting between the two blocks is

• A. $8\text{N}$
• B. $10\text{N}$
• C. $6\text{N}$
• D. $4\text{N}$

Answer 1

The correct option is A $8\text{N}$

Assuming both the blocks move together
Acceleration of system $=\frac{20-2}{4+2}=3{\text{ms}}^{-2}$
For upper block w.r.t. lower block


$f=F_1+ma=2+2\left(3\right)=8\text{N}$
For upper block limiting friction is $f_L=\mu mg=10N$
As $f<f_L$, upper block will not slip over second block ie both the blocks will move together.