Question

A balloon is rising vertically upwards at a velocity of $10m/s$ . When it is at a height of $45m$ from the ground,a parachutist bails out from it. After $3seconds$ he openshis parachute and decelerates at a constant rate of $5m/s^{-2}$. What was the height of the parachutist above the ground when he opened his parachute?(take $g=10m/s^{-2})$

• A. 15 m
• B. 30 m
• C. 45 m
• D. 60 m

Answer 1

Answer: (B)

30 m

Given,

$u=10m/s$ in upward direction.

$g=-10m/s^2$ in downward direction

$t=3sec$

$H=45m$

So by second equation of motion:

$s=ut+\frac{1}{2}a{t}^2$

$=10\times 3+\frac{1}{2}(-10)\times 3\times 3$

$=30-45$

$=-15m$

Here negative sign indicates that it is directed downwards.

So height from the ground when he opened parachute is $=45-15=30m$