Question

A balloon is flying up with a constant velocity of 5m/s. At a height of 100m, a stone is dropped from it. At the instant the stone reaches the ground level, the height of the balloon will be? ?

Answer 1

Velocity of balloon =5m/s
The stone when dropped its initial velocity=5m/s.
But it is downward in direction,so initial velocity= -5m/s.
Height of balloon from ground=100m.
By the equation ,
h=-ut+1/2 gt^2
h=height
u=initial velocity
g=accelaration due to gravity=9.8~ 10
t=time.
100=-5t+10/2 t^2
20=-t+t^2
t^2 - t - 20=0
t^2 - 5t + 4t - 20 =0
t(t-5) + 4(t-5)=0
(t-5)(t+4)=0
there for t=5 sec.
time can not be negative so we neglect t=-4.
The balloon is moving with constat velocity so,
S=V×t
S= distant
V=velocity
t=time.
There for
S=5×5=25m.

The balloon will move 25m from the initial position.
so,total height=100+25=125m.