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?

1 Answer
Jan 1, 2017

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#