If the water falls from a dam into a turbine wheel $19.6 \ m$ below,then the velocity of water at the turbines is .................. $m/s$ (take $g = 9.8 \ m/s^2$).

$A$ stone thrown upward with a speed $u$ from the top of a tower reaches the ground with a velocity $4 u$. The height of the tower is .........

$A$ ball is thrown upwards. Its height varies with time as shown in the graph. If the acceleration due to gravity is $g = 7.5\, m/s^2$,then the height $h$ is.........$m$.

Two bodies $A$ (of mass $1\,kg$) and $B$ (of mass $3\,kg$) are dropped from heights of $16\,m$ and $25\,m$ respectively. The ratio of the time taken by them to reach the ground is:

Can a particle moving in a straight line have zero velocity and non-zero acceleration at any instant? Give an example.

$A$ stone is dropped from a building of height $h$ and it reaches the ground after $t$ seconds. From the same building,if two stones are thrown (one upwards and one downwards) with the same velocity $u$ and they reach the earth's surface after $t_1$ and $t_2$ seconds respectively,then: