Conservation of Energy on Inclined Plane

[lajohn]

Hi, I am confused about something.

I understand how one gets the equation 1/2kx^2=mgh, and so if 1/2kx^2=0, then mgh=0, but this doesn't make sense to me. Isn't it true the energy is converted, so it's impossible to have both equal zero? One could equal zero, and the other would be at a max, or vice versa on the other end of the spectrum, but not BOTH equal zero?

 

[HallsofIvy]

It would be nice to tell us what you are talking about!

I assume that you have a spring since you have "1/2 k x²", the work necessary to compress a spring a distance x from its equilibrium position and so the potential energy there (relative to at the equilibrium position). Clearly mgh is the potential energy due to height h above some reference point. You say "I understand how one gets the equation 1/2kx^2=mgh" but I don't even understand what it MEANS since you haven't told us where the reference point is or how x is connected to h.

 

[pmrazavi]

in the equation: .5kx^2=mgh, notice that both of these energies are not for the initial or the final point, the left side is the energy of the start point that we only got spring, and the right side is mgh, which is in the final place and there is no spring...
i hope I've understood your question correctly..