$A$ horizontal bridge is built across a river. $A$ student standing on the bridge throws a small ball vertically upwards with a velocity $4\,m s^{-1}$. The ball strikes the water surface after $4\,s$. The height of the bridge above the water surface is $......\,m$ (Take $g=10\,m s^{-2}$).

$A$ ball is thrown vertically upwards. Which of the following plots represents the speed-time graph of the ball during its flight if air resistance is not ignored?

$A$ boy standing at the top of a tower of $20 \, m$ height drops a stone. Assuming $g = 10 \, m/s^2$,the velocity with which it hits the ground is ......... $m/s$.

When a particle is thrown vertically upwards,its velocity at one third of its maximum height is $10 \sqrt{2} \, m/s$. The maximum height attained by it is .......... $m$.

$A$ ball is thrown vertically upward from the ground at time, $t=0 \,s$. It passes the top of a tower at $t=3 \,s$ and $2 \,s$ later it reaches its maximum height. The height of the tower is (Acceleration due to gravity, $g=10 \,m/s^2$) (in $\,m$)

$A$ ball falls vertically downward and bounces off a horizontal floor. The speed of the ball just before reaching the floor $(u_1)$ is equal to the speed just after leaving contact with the floor $(u_2)$,where $u_1 = u_2$. The corresponding magnitudes of accelerations are denoted respectively by $a_1$ and $a_2$. The air resistance during motion is proportional to speed and is not negligible. If $g$ is the acceleration due to gravity,then: