Two stones are thrown up simultaneously from the edge of a cliff $240\ m$ high with initial speed of $10\ m/s$ and $40\ m/s$ respectively. Which of the following graph best represents the time variation of relative position of the second stone with respect to the first ?

(Assume stones do not rebound after hitting the ground and neglect air resistance, take $g = 10\ m/ s^2$)
(The figures are schematic and not drawn to scale)

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

A ball is thrown vertically upwards from the top of a tower at $4.9\,\,m{s^{ – 1}}$. It strikes the pond near the base of the tower after $3 $ seconds. The height of the tower is……..$m$

A ball is dropped from the top of a building $100\,m$ high. At the same instant another ball is thrown upwards with a velocity of $40\,m / s$ from the bottom of the building. The two balls will meet after $……….\,s$

Aball is thrown vertically down with velocity of $5m/s$. With what velocity should another ball be thrown down after $2$ seconds so that it can hit the $1^{st}$ ball in $2$ seconds………$m/s$