a ball is thrown vertically upward with velocity 'u' from a balloon  descending with velocity 'v'.the ball will pass by the balloon after time:

answer:2(u-v)/g

Now  here it is given that vel of ball = um/s^2

with respect to the balloon so its vel with respect to ground

u1 = (u - v)m/s^2

and apply eqn then =

then now s = 0 so

0 = (u-v)t - 1/2gt^2 so

now t = 2(u-v)/g

i hope i am correct

best of luck

plz mention velocity "u" of ball is its absolute velocity(relative to ground) or it is velocity relative to ballon.

if it is relative to ground then we can write eq of path of ball as

x=ut-gt²/2

and for ballon

x=-vt

taking downward direction -ve and upward+ve

when the ball will pass by the balloon they will be at same height  let that height be z

putting z in both equations and equating

-vt=ut-gt²/2

so answer shouid be

T=2(V+u)/g