velocity of object just before hitting the ground = 10 m/s
10 m/sExplanation:
here's the solution : -
=》mechanical energy is always constant, when the object is at the top of the building , the object has potential energy but no kinetic energy,
so, at the top of the building the mechanical energy = potential energy = 100 J
but at when it is dropped from the building, the whole potential energy get converted into kinetic energy, just before reaching the bottom .
so, mechanical energy in the object just before hitting the ground = kinetic energy
( potential energy = 0 )
So, kinetic energy = 100 J
now, we know

=》

( since, mass = 2 kg )
=》

=》

=》

so, velocity of object just before hitting the ground = 10 m/s