A balloon is going vertically upward with a velocity of 15 `ms^-1`. When it is at a height of 50 m above the ground a stone is gently dropped from it. The stone will reach the ground in time (take g = 10 `ms^-2)`:

Options

A. 5 s
B. 7 s
C. 9 s
D. 3 s

Answer

a

Explanation

h=ut+`(1)/(2)g t^(2)` Since ballon is going vertically up.
`:.` Take u as -ve.50=-`15xxt+(1)/(2)10.t^(2)`
`implies 5t^(2)-15t-50=0`
`implies5t^(2)-15t-50=0`
`implies t^(2)-3t-10=0`
`implies t=5 s`