# Conservation of Mechanical Energy

Conservation of Mechanical Energy

In this section, we examine what happens to this mechanical energy when only conservative forces cause energy transfers within the system-that is, when frictional
and  forces do not act on the objects in the system.

In an isolated system where only conservative forces cause energy changes, the kinetic energy and potential energy can change, but their sum, the mechanical energy Ernest of the system, cannot change.

This result is called the principle of conservation of mechanical energy. (Now you can see where conservative forces got their name.) With the aid of we can write this principle in one more form.

When mechanical energy of a system is conserved, we can relate the sum of kinetic energy and potential. In olden days, a native Alaskan wouldbe tossed via a blanket to be able tosee farther over the flat terrain. Nowadays,it is done just for fun. During theascent of the child in the photograph. shows an example in which the principle of conservation of mechanicalenergy can be applied: As a pendulum swings, the energy of the pendulum-Earth system is transferred back and forth between kinetic energy K and gravitationalpotential energy V, with the sum K + V being constant. If we know the gravitationalpotential energy when the pendulum bob is at its highest point gives us the kinetic energy of the bob at the lowest point shows an example in which the principle of conservation of mechanicalenergy can be applied: As a pendulum swings, the energy of the pendulum-Earth system is transferred back and forth between kinetic energy K and gravitationalpotential energy V, with the sum K + V being constant. If we know the gravitationalpotential energy when the pendulum bob is at its highest pointgives us the kinetic energy of the bob at the lowest point

CHECKPOINT 3: The figure shows four situations-one in which an initially stationary block is dropped and three in which the block is allowed to slide down friction less ramps. ·(a) the situations according to the kinetic energy of the block at point B, greatest first. (b) Rank them according to the speed of the block at point B, greatest. 