From ground a balloon starts ascending at a constant speed of `25 m//s`. After 5 sec. a bullet is short vertically upwards from the ground. The minimum speed of bullet at which it is able to hit the balloon will be:

Options

A. `0 m//s`
B. `50 m//s`
C. `75 m//s`
D. `25 m//s`

Answer

C

Explanation

analysing motion of bullet w.r. to balloon we use.
`V_("Bullet Balloon") = U - 20]`
`a_(B) rArr -g = - 10 m//s^(2)`
`U_(1)` should be such that it will reach

to a minimum height of `125 m` at this height `v_(F)` of Bullet `= 0`
so `125 = ((U - 25)^(2))/(2g)`
`U = 75 m//s`