Three blocks of masses `3kg ,2kg` and `1kg` are placed side by side on a smooth surface as shown in figure. A horizontal force of `12N` is applied on `3kg` block. Find the net force on `2kg` block.

Explanation

Since all the blocks will move with same acceleration(say a) in horizontal direction .Let us take all the blocks as a single system.

Net external force on the system is `12N` in horizontal direction.
Using `sumF_(x)=ma_(x),`
we get , `12=(3+2+1)a=6_(a)`
or `a=(12)/(6)=2m//s^(2)`