A helicopter is ascending vertically with a speed of 8.0 `ms^(-1)` .At a height of 120 m 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 `implies` s=-120 m
`s=ut+(1)/(2)at^(2)-120=8t-(1)/(2)xx9.8xxt^(2)-8t-120=0`
`t=(8pmsqrt(64+4xx4.9xx120))/(2xx4.9)=(8pmsqrt(2416))/(9.8)=(8pm49.15)/(9.8)`
`t=(8pm49.15)/(9.8)` ,(only positive value)=5.83 sec