A body is dropped from the top of a tower. If its average velocity, when it reaches the ground, is $10 \mathrm{m} {\mathrm{s}}^{-1}$and the time taken by it to reach the ground is $2 \mathrm{s}$; the height of the tower is _____ $\mathrm{m}$.

A vehicle travels along a straight path between two places $\alpha$ and $\beta$. It travels first half of the distance with a velocity of $72 \mathrm{km} {\mathrm{h}}^{-1}$ and the remaining distance with a velocity of $36 \mathrm{km} {\mathrm{h}}^{-1}$. Then the average velocity of the vehicle is _____ $\mathrm{m} {\mathrm{s}}^{-1}$.

A car is moving along a semicircular track as shown in the figure in a duration of $2 \mathrm{\pi }$ second from P to Q, then choose the correct statement(s).