# Energy method

## Main Question or Discussion Point

While solving classical mechanics problems there is a wide feeling that

energy methods can be used to solve any problem.

What is energy method. How is it different from other methods?

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robphy
Homework Helper
Gold Member
Here's a problem that is more easily solved with an energy method: the roller coaster.
For simplicity, consider a point particle on a frictionless roller coaster track. With Newtonian methods, you need to know the net force on the particle to determine its acceleration (and its initial conditions to determine the motion). However, the net force varies along the track since the free-body diagram varies. By hand, this approach is tedious to calculate the whole motion. One could use a computer to carry out the calculation. An energy method using the "Conservation of Total Energy" makes the problem much simpler.

Examples of energy methods: virtual work, Lagrange Eqs, Hamilton Eqs, etc.
However, these energy methods have limitations as well.

any web on this?