Question

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 $g=10\, m/s^2$)

• A.
• B.
• C.
• D.

Answer 1

Answer: (C)

Answer 2

$I\,st$ stone
$0 \leq t \leq 8$ sec
$v_{r}=40-10$
$=30 \,m / s$
$a_{r}=0$

$s_{r}=v_{r} \times t=30 \times 8=240\, m$

$8$ sec $< t \leq 12$ sec
$v _{ r }$ increases in magnitude and relative acceleration is $g$ downwards