For instance, compress a spring. Another example is the gravitational field of the Earth. If you lift an object up, you've just stored energy in earth's gravitational field. Now this tells us how much work we have to do. Use the diagram below and consider it frictionless.
C Now substitute in the values for v B , h B , h C , and solve for v C .
I'll let you guys fly solo on this one. Because the energy at A and C must be the same also. Now, finally, Conservation of Energy . The total mechanical energy we looked at above now changes at a later time or position because energy was lost to friction. We can use Conservation of Energy.