$A$ ball is dropped from a high-rise platform at $t=0$ starting from rest. After $6$ seconds,another ball is thrown downwards from the same platform with a speed $v$. The two balls meet at $t=18\,s$. What is the value of $v$ in $m/s$? (Take $g= 10\,m/s^2$)

From the top of a tower,a ball is thrown vertically upward which reaches the ground in $6 \, s$. $A$ second ball thrown vertically downward from the same position with the same speed reaches the ground in $1.5 \, s$. $A$ third ball released from rest from the same location will reach the ground in ........ $s$.

$A$ body falling freely under gravity passes two points $30 \ m$ apart in $1 \ s$. From what point above the upper point did it begin to fall? (Take $g = 10 \ m \ s^{-2}$)

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 projected from the ground vertically upward is at the same height at times $t_1$ and $t_2$. The speed of projection of the ball is [Neglect the effect of air resistance].

$A$ stone is thrown vertically up from the top end of a window of height $1.8 \,m$ with a velocity of $8 \,m/s$. The time taken by the stone to cross the window during its downward journey is (Acceleration due to gravity $= 10 \,m/s^2$) (in $\,s$)