A ball is dropped from a balloon going up at a speed of 7 m/s. If the balloon was at a height 60 m at the time of dropping the ball, how long will the ball take in reaching the ground?
Height of the balloon from the ground, s = 60 m
Balloon is moving upwards with velocity 7 m/s.
The balloon and the ball are moving upwards with the same speed.
When the ball is dropped, its initial velocity (u) is −7 m/s.
Acceleration due to gravity, a = g = 9.8 m/s2
Using the equation of motion, we have:
s=
60=-7t+
×9.8×
⇒60=-7t+4.9×
⇒4.9
-7t-60=0
=>49t2-70t-600=0 (multiplying both side by 10)
=>49t2+140t-210t-600=0
=>7t(7t+20)-30(7t+20) = 0
=>(7t+20)(7t-30)=0
either 7t+20=0 or 7t-30=0
S0; 
---------- (i)
------------- (ii)
The value of t cannot be negative. So, we will take equation (ii)
So, 