An object is thrown vertically upward with a speed of $30 \,m/s$. The velocity of the object half-a-second before it reaches the maximum height is (in $\,m/s$)

$A$ balloon rises from rest with a constant acceleration $g/8$. $A$ stone is released from it when it has risen to height $h$. The time taken by the stone to reach the ground is

$A$ particle is dropped under gravity from rest from a height $h$ $(g = 9.8 \ m/s^2)$. If it travels a distance of $9h/25$ in the last second of its motion,the height $h$ is ......... $m$.

$A$ ball is dropped from a bridge that is $45 \ m$ above the water. It falls directly into a boat which is moving with constant velocity. The boat is $12 \ m$ away from the point of impact when the ball is dropped. The speed of the boat is (Take $g=10 \ m \ s^{-2}$) (in $m \ s^{-1}$)

Two bodies of masses $1 kg$ and $5 kg$ are dropped gently from the top of a tower. At a point $20 cm$ from the ground,both the bodies will have the same

If a particle takes $t$ seconds less and acquires a velocity of $v \ ms^{-1}$ more in falling through the same distance (starting from rest) on two planets where the accelerations due to gravity are $2g$ and $8g$ respectively,then $v=$