Two balls $A$ and $B$ are placed at the top of $180 \,m$ tall tower. Ball $A$ is released from the top at $t =0 \,s$. Ball $B$ is thrown vertically down with an initial velocity $u$' at $t=2\, s$. After a certain time, both balls meet $100 \,m$ above the ground. Find the value of $u$ in …………… $ms ^{-1}$. [use $g =10 \,ms ^{-2}$ ]

Two spheres of same size one of mass $2\, kg$ and another of mass $4\, kg$ are dropped simultaneously from the top of Qutab Minar(height $= 72\,m$). When they are $1\,m$ above the ground, the two spheres have the same

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.

A ball is dropped downwards. After $1$ second another ball is dropped downwards from the same point. What is the distance between them after $3\, seconds$………..$m$

From the top of a $64\, ft$ high tower, a stone is thrown upwards vertically with the velocity of $48\, ft/s$. The greatest height (in $ft$) attained by the stone, assuming the value of the gravitational acceleration $g\, = 32\, ft/s^2$, is