Question

Two blocks of mass $2kg$ and $4kg$ are kept in contact with each other on a smooth horizontal surface. A horizontal surface of $10N$ is applied on the first bock due to which they move with certain constant acceleration.

Answer 1

FBD

Let $a=$ common acceleration of blocks, $R=$ Force between the two blocks

From $FBD$ of block $1$

$F-R=m_{1}a$ ...$\left(i\right)$

From $FBD$ of block $2$,

$R=m_{2}a$ ...$\left(ii\right)$

$\therefore$ From $\left(i\right)$ & $\left(ii\right)$, $F=(m_1+m_2).a$

$\therefore a=\frac{F}{m_1+m_2}=\frac{12}{6}=2m/se{c}^2$

$\therefore$ Force between blocks $R=m_{2}a=(4\times 2)N=8N$.