Question

A parachutist after bailing out falls for $10$ s without friction. When the parachute opens he descends with an acceleration of $2m/s^2$ against his direction and reached the ground with $4$ $m/s$. From what height he has dropped himself? $(g=10m/s^2)$

• A. $500$ m
• B. $2496$ m
• C. $2996$ m
• D. $4296$ m

Answer 1

Answer: (C)

$2996$ m

$u=gt\Rightarrow u=10g$
$h_1=\frac{1}{2}g{t}^2$
$h_2=\frac{v^2-u^2}{-2a}$
total height $=h_1+h_2$

$v=g{t}_1(100{)}^2=u^2+2\times 10S_1$
$v=10\times 10=100m/s.[S_1=500mt]$
$4=100-2t_2$
$t_2=48sec$
$\Rightarrow S_2=100t_2-1/2\times 2t_2^2$
$=4800-(48{)}^2$
$=2496$ mt.
$S_1+S_2=2996$ mt