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/s2)

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/s2) (A)  (B)  (C)  (D)

Tardigrade Admin · Accepted Answer

I st stone 0 ≤ t ≤ 8 sec vr=40-10 =30 m / s ar=0

sr=vr × t=30 × 8=240 m

8 sec < t ≤ 12 sec v r increases in magnitude and relative acceleration is g downwards

Ist stone 0≤t≤8 sec vr​=40−10 =30m/s ar​=0 sr​=vr​×t=30×8=240m 8 sec <t≤12 sec vr​ increases in magnitude and relative acceleration is g downwards

$I s t$ 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