$A$ ball is thrown vertically upwards with a velocity of $19.6 \, m/s$ from the top of a tower. The ball strikes the ground after $6 \, s$. The height from the ground up to which the ball can rise is given by $\left(\frac{k}{5}\right) \, m$. The value of $k$ is ..... (use $g = 9.8 \, m/s^2$)

Two balls $A$ and $B$ are thrown with the same velocity $u$ from the top of a tower. Ball $A$ is thrown vertically upwards and ball $B$ is thrown vertically downwards. If a ball $C$ is thrown with the same velocity $u$ in the horizontal direction from the top of the tower,and if $t_A = 6 \ s$ and $t_B = 2 \ s$,then the time $t_C$ taken by ball $C$ to reach the ground is equal to........$s$.

Two balls are dropped from heights $h$ and $2h$ respectively from the Earth's surface. The ratio of the time taken by these balls to reach the Earth is

$Assertion$ : $A$ body can have acceleration even if its velocity is zero at a given instant of time.
$Reason$ : $A$ body is momentarily at rest when it reverses its direction.

$A$ body is projected vertically upwards with a velocity $u$. It passes through a certain point above the ground after $t_1$ seconds. The time interval after which the body passes through the same point during the return journey is

$A$ stone is thrown vertically upwards with a velocity $V_0$ from a tower of height $h$ and it reaches the ground in time $t_1$. If the stone is thrown downwards with the same velocity $V_0$ from the same tower,it reaches the ground in time $t_2$. If the stone is dropped from the tower,it reaches the ground in time $t$. Find the value of $t$.