A free-falling object, m=30kg, falls from the ground 10m, and falls to the ground 4m. How to write Ek and EP?
If the ground is regarded as the zero point of potential energy
Ep=mgh=30×4×g= 120g
Ek0+Ep0=Ek+Ep
30× 10g=30×4g+Ek
Ek= 180g
The value of g depends on the requirements of the topic.