Question

an 80kg man jumps off a 60m cliff, halfway to the ground, his GPE is 27,072J. What is his KE at the same moment?

Answer 1

Half way down is 30 m down.

Assuming the GPE reference is at the bottom of the cliff, then
GPE=mg(30)=27072 J
KE=(1/2)mv²

Equate GPE and KE.