An object is thrown vertically upwards. At its maximum height,which of the following quantities becomes zero?

If a stone thrown vertically upwards from a bridge with an initial velocity of $5 \,m \,s^{-1}$ strikes the water below the bridge in a time of $3 \,s$, then the height of the bridge above the water surface is (Acceleration due to gravity $= 10 \,m \,s^{-2}$) (in $\,m$)

$A$ body dropped from the top of a tower falls through $40 \; m$ during the last two seconds of its fall. The height of the tower is ..... $m$.

$A$ player throws a ball upwards with an initial speed of $29.4 \; m s^{-1}$. To what height does the ball rise and after how long (in seconds) does the ball return to the player's hands? (Take $g = 9.8 \; m s^{-2}$ and neglect air resistance).

$A$ parachutist after bailing out falls $50\, m$ without friction. When the parachute opens,it decelerates at $2\, m/s^2$. He reaches the ground with a speed of $3\, m/s$. At what height did he bail out (in $, m$)?

An object is projected upwards from the foot of a tower. The object crosses the top of the tower twice with an interval of $8 \ s$ and the object reaches the foot again after $16 \ s$. The height of the tower is [ $g = 10 \ m/s^2$ ]. (in $m$)