Question

A ball is dropped from a balloon going up at a speed of 7m/s. If the balloon was at a height of 60m at the time of dropping the ball, how long will the ball take in reaching the ground?

Answer 1

Given,

$Speed=7m/s$

$height=60m$

So, initially, the ball is going the upward,

$u=-7m/s,s=60m,a=g=10m/s^2$

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

$60=-7t+\frac{1}{2}10t^2$

$5t^2-7t-60=0$

$t=\frac{7\pm \sqrt{49+4\times 5\times 60}}{2\times 5}$

$t=\frac{7\pm 35.34}{10}$

Taking $+ve$ sign then we get,

$t=\frac{7\pm 35.34}{10}=4.2s$

Thus, the ball will take time in reaching the ground is:

$4.2s$