Notam cu h1 inaltimea cautata. h=5m, Energia cinetica Ec, Energia potrentiala Ep
La inaltimea h1: Ec=2Ep Ec=mv²/2; Ep=mgh1;
Conform relatiei lui Galilei
v²=2g(h-h1).
mv²/2=2mgh1
v²/2=2gh1
2g(h-h1)=2gh1
h-h1=h1
2h1=h
h1=h/2
h1=2,5m.
v²=4gh1
v²=4×10×2,5
v=10m/s²