NUMERICAL QUESTION BASED ON THE MOTION UNDER GRAVITY

Assume upward direction is positive and downward direction is negative.

1.In this case if the balloon is ascending initial velocity is u = +5m/s

h = -300m, a = -9.8m/s^2.

use s = ut+1/2at^2 and solve t.

2. when the balloon descends initial velocity u = -5m/s as this is in the downward direction.

Let us take upward direction as positive and downward direction as negative.

 s=ut+1/2at^2 to find t.

3. here take u =0 and then solve for t.