Consider two masses m1 and m2 at the top of two frictionless inclined planes. Both masses start from rest at the same height. However, the plane on which m 1 sits is at an angle of 30e with the horizontal, while the plane on which m2 sits is at 60e. If the masses are released, which is going faster at the bottom of its plane?

The work-energy principle:  The net work done on an object is equal to the change in the object's kinetic energy.

The principle of conservation of mechanical energy for conservative forces: If only conservative forces are acting, the total mechanical energy of a system neither increases nor decreases in any process. It stays constantπit is conserved.
The law of conservation of energy: The total energy is neither increased nor decreased in any process. Energy can be transformed from one form to another, and transferred from one object to another, but the total amount remains constant.