Question

A balloon starts rising from ground with an acceleration of $1.25m/{\sec }^2$. After $8$ seconds a stone is released from the balloon. The maximum height from the ground reached by stone will be

• A. 40 m
• B. 50 m
• C. 45 m
• D. 55 m

Answer 1

Answer: (C)

When a particle separates from a moving body it retains the velocity of the body but not its acceleration.

At the instant of released the balloon is

$s=\frac{1}{2}\times (1.25)\times 64=40m$

above the ground and is having an upward velocity

$=1.25\times 8=10m/\sec$.

For the motion of stone from the balloon to the highest point,

$u=10m/s$.

$a=-g=-10m/s^2$

$v=0$ using $v^2-u^2=2as$

$0-100=-2\times 10\times s$

$s=5$ metres

$\therefore$ maximum height from ground

$=40+5=45m$