A block `B` is placed on the block `A`.The mass of block `B` is less than the mass of block `A`. Friction exists between the blocks , whereas the ground on which block `A` is placed is taken to be smooth. A horizontal force `F`, increasing linearly with time begins to act on `B`. The acceleration `a_(A)` and `a_(B)` of blocks `A` and `B`, respectively , are plotted against `t`. The correctly plotted graph is

Options

A.
B.
C.
D.

Answer

C

Explanation

Block `A` is ………………
The two blocks will move together with the same acceleration as long as the force of friction between them is less than the limiting friction, as the only force on the lower block `B` is the force of friction. One limiting friction is reached, the acceleration of `B` becomes constant `(= (F_(lim))/("mass of B"))` , and the acceleration of `A` continues to increase at a faster rate.