JEE Mains Model Paper 21

A small block of mass 1 kg is placed over a plank of mass 2 kg. The length of the plank is 2 m. Coefficient of friction between the block and the plank is 0.5 and the ground over which plank is placed is smooth. A constant force F = 30 N is applied on the plank in horizontal direction. The timeafter which the block will separate from the plank is (g = 10 m/s2)