Two blocks of masses m m\,m kg and 3m kg are in contact on a smooth horizontal surface. A horizontal force of magnitude P P\,P N is applied to the block of mass m m\,m so that it pushes the other block.
Show that the acceleration of the system is P4m m s−2\dfrac{P}{4m}\text{ m s}^{-2}4mP m s−2.
Show that the contact force between the blocks is 3P4\dfrac{3P}{4}43P N.
The same force is instead applied in the opposite direction to the block of mass 3m, so that the larger block pushes the smaller block. Find the new contact force.