A helicopter is ascending vertically with a speed of `8.0 ms^(-1)`. At a height of 120m above the earth , a package is dropped from a window . How much time does it take for the package to reach the ground ?

Explanation

`u=8 m//s, "height" h = 120m rArr s=-120m`
`s=ut+1/2at^(2) -120=8t-1/2xx9.8xxt^(2)-8t-120=0`
`t=(8+-sqrt(64+4xx4.9xx120))/(2xx4.9)=(8+-sqrt(64+2352))/(9.8)=(8+-sqrt(2416))/(9.8)=(8+-49.15)/(9.8)`
`t=(8+-49.15)/(9.8)` , (only positive value )`=5.83 sec`