An object falls freely fr a height of 25m onto the roof of a building 5m high. Calculate the velocity with which the object strikes the roof (g=10ms-¹)

The object falls from a height of $25\,\mathrm{m}$ (above ground) onto the roof at $5\,\mathrm{m}$ (above ground).
Thus, distance fallen $s=25-5=20\,\mathrm{m}$.
Initial velocity $u=0\,\mathrm{m\,s^{-1}}$ (freely falling from rest).
Acceleration $a=g=10\,\mathrm{m\,s^{-2}}$.

20 \ m,s^{-1}