A block is placed on a rough horizontal plane. A time dependent horizontal force $F = kt$ acts on the block, where $k$ is a positive constant. The acceleration - time graph of the block is

If a force of $250\, N$ act on body, the momentum acquired is $125\, kg-m/s$. What is the period for which force acts on the body  ......... $\sec$

When a bus suddenly takes a turn, the passengers are thrown outwards because of

A girl riding a bicycle along a straight road with a speed of $5\,ms^{-1}$ throws a stone of mass $0.5\, kg$ which has a speed of $15\,ms^{-1}$ with respect to the ground along her direction of motion. The mass of the girl and bicycle is $ 50\, kg$. Does the speed of the bicycle change after the stone is thrown ? What is the change in speed, if so ?

$100$ balls each of mass moving with speed $v$ simultaneously strike a wall normally and reflected back with same speed, in time $t s$. The total force exerted by the balls on the wall is

A body of mass $3\, kg$ hits a wall at an angle of $60^o$ and returns at the same angle. The impact time was $0.2 \;.s$ Calculate the force exerted on the wall