Question

An object is thrown vertically upward from a height of `2 m` at `1 m/s`. How long will it take for the object to hit the ground?

Answer 1

The initial velocity of the object in upward direction `u=1m/s`
( upward direction is taken positive )

So the downward acceleration due to gravity `g=-9.8m/s^2`

The object is thrown from height `2m`. If it reaches ground after`ts` then the displacement of the object during `t s` will be `h=-2m`
Hence applying equation of kinematics for under gravity motion we can write
`h=uxxt+1/2xxgxxt^2`

`=>-2=1xxt-1/2xx9.8xxt^2`

`=>4.9t^2-t-2=0`

`=>t=(1+sqrt((-1)^2-4xx4.9xx(-2)))/(2xx4.9)~~0.75s`