A 40 kg block is resting at a height of 5 m off the ground. If the block is released and falls to the ground, what is its total energy at a height of 2m (g=10m/s²)?

For such questions we have to use the idea of conservation of energy, 

i.e. total energy will be same throughout the path.

So, total energy at highest point =E = PE + KE = mgh

(KE = 0, as the object is at rest)

Therefore, E = mgh = 40 x 10 x 5= 2000 Joules or 2 Kilo Joules.

Since total energy remains constant , hence at height 2m from the ground the energy is 2000 Joules