Kinetic Plus Potential Energy

Can KE (1/2M×V2) + PE (MGH) = the total amount of energy in a object? Also, is this another way to work out the famous equation E=MC2?
- Jess (age 13)
Sydney, NSW, Australia

That expression can work for the total energy in some limited circumstances.

1. Nothing major (e.g. nuclear reactions) happens to change M, so you can ignore the rest energy.

2. There's a uniform gravitational field g so you can write the gravitational potential energy in that simple form.

3. The speed v is much less than c and you don't consider any distances with gh comparable to c², so you can ignore relativistic effects.

E=mc² is not especially hard to work out, but these equations definitely are not the path to get there.

Mike W.

(published on 07/30/2013)