Question

A balloon starts from the ground and moves vertically upwards with an acceleration of 2
m/s. After 5s, a stone is released from the balloon. Find the time taken by the stone to reach the
ground​

Answer 1

ATQ;

In balloon: u=0m/s

                  acc.=2m/s^2

                  t=5s

So, the height that the balloon will reach;

s=ut+1/2at^2

=(0m/s)*(5s)+(1/2*2m/s^2*5s*5s)

 =0+25m

 =25m

When stone is released:

s=25m                                                                                              acc.=-2m/s^2 (as acceleration due to gravity is opposite)                               v=0 (as it will fall on the ground)

Therefore, u=?

So, v^2-u^2=2a

=>0-u^2=2*(-2m/s)*25ms

 =>-u^2=-100m/s

 =>u=10m/s

So, the time would be taken by the stone to reach the ground is

=>t = (v-u)/acc.

     =  {0-(-2)}/2

     = 2/2  

     = 1sec.