$A$ stone falls from the top of a tower of height $100 \text{ m}$ and at the same time another stone is projected vertically upwards from the ground with a velocity $25 \text{ m/s}$. The two stones meet after (in $\text{ s}$)

$A$ bus starts moving with an acceleration of $2\,m/s^2$. $A$ cyclist,$96\,m$ behind the bus,starts moving simultaneously towards the bus at a constant speed of $20\,m/s$. After how many seconds will the cyclist be able to overtake the bus?

Explain the concept of relative velocity and its two cases.

Explain the concept of relative displacement and its various cases.

Train $A$ is moving along two parallel rail tracks towards north with speed $72 \ km/h$ and train $B$ is moving towards south with speed $108 \ km/h$. The velocity of train $B$ with respect to $A$ and the velocity of the ground with respect to $B$ are (in $ms^{-1}$):

Two bodies start moving from the same point along a straight line with velocities $v_1 = 6 \, m/s$ and $v_2 = 10 \, m/s$,simultaneously. After what time will their separation become $40 \, m$?