A lift is moving down with acceleration $a$. A man in the lift drops a ball inside the lift. The acceleration of the ball as observed by the man in the lift and a man standing stationary on the ground are respectively:

A body hangs from a spring balance supported from the roof of an elevator upwards with an acceleration of $4.9 \mathrm{m}/{\mathrm{s}}^2$. The balance reads $30 \mathrm{kg}$. The mass of the body is

A boy whose mass is $40 \mathrm{kg}$, is standing in a lift. The force felt by the feet of the boy will be maximum when the lift:

A monkey is descending along the branch of a tree with constant acceleration. The breaking strength of the branch is $75\%$of the weight of the monkey. The minimum acceleration with which the monkey can slide down without breaking the branch is

An empty car is moving with velocity $u$ on a smooth road can be stopped in a distance $s$ by applying brakes. If the passengers add $40\%$ to its weight and the braking force remains the same, the stopping distance for the same velocity $u$ is:

Consider a car moving on a straight road with a speed of $100 \mathrm{m}/\mathrm{s}$. The distance at which the car can be stopped is $\left({\mu }_k=0.5\right)$,$\left(g=10 \mathrm{m}/{\mathrm{s}}^2\right)$

Sand is being dropped on a conveyor belt at the rate of $M \mathrm{kg}/\mathrm{s}$. The force necessary to keep the belt moving with a constant velocity of $v \mathrm{m}/\mathrm{s}$ will be:

A $10 \mathrm{g}$ ball falls vertically on a surface at a speed of $5 {\mathrm{ms}}^{-1}$ and rebounds with the same speed. The ball remains in contact with the surface for $0.01 \mathrm{s}$. The average force exerted by the surface on the ball is:

A cricketer catches a $150 \mathrm{g}$ ball moving at a speed of $20 {\mathrm{ms}}^{-1}$. If he completes the catching process in $0.1 \mathrm{s}$, the force exerted by the ball on his hands is: