Two balls $A$ and $B$ are thrown with same velocity $u$ from the top of a tower. Ball $A$ is thrown vertically upwards and the ball $B$ is thrown vertically downwards. If $t_A = 6\  s$ and $t_B = 2\ s$ then velocity $u$ of each ball is…….$ms^{^{-1}}$

A player throws a ball upwards with an initial speed of $29.4 \;m s^{-1}$. What is the direction of acceleration during the upward motion of the ball?

A stone is allowed to fall from the top of a tower $100\,\,metre$  high and at the same time another stone is projected vertically upwards from the ground with a velocity of $25\,\,ms^{-1}.$  The two stones will meet after………$s$

A ball is thrown up vertically with a certain velocity so that, it reaches a maximum height $h$. Find the ratio of the times in which it is at height $\frac{ h }{3}$ while going up and coming down respectively.

Reaction time : When a situation demands our immediate action, it takes some time before we really respond. Reaction time is the time a person takes to observe, think and act. For example, if a person is driving and suddenly a boy appears on the road, then the time elapsed before he slams the brakes of the car is the reaction time. Reaction time depends on complexity of the situation and on an individual.

You can measure your reaction time by a simple experiment. Take a ruler and ask your friend to drop it vertically through the gap between your thumb and forefinger . After you catch it, find the distance $d$ travelled by the ruler. In a particular case, $d$ was found to be $21.0\; cm$. Estimate reaction time in second.