- #1
flyingpig
- 2,579
- 1
Homework Statement
This is the conservation of energy in the absence of external forces
ΔKE + ΔPE + ΔTE + ΔU= 0
TE is friction, U is other internal energy, like the spring
So expand and disregard U and TE for a moment
½m(v² - v₀²) + mg(h - h₀) = 0
Now comes the question, why is + mg(h - h₀) and not -mg(h - h₀)? Is gravitational potential energy not the same thing as the work done by gravity? Because gravity pulls down and if you go up, that's negative work. I've used the equation (with the positive mgh) many times and have not failed me.