Module 6—Work and Energy

Explore

 

Mechanical Energy

 

When a skier is moving down the slopes of a mountain, he or she has two forms of energy—potential and kinetic. The sum of the potential energy and the kinetic energy is called mechanical energy. Expressed as an equation, it is as follows:

 

Em = Ep + Ek

 

Quantity	Symbol	SI Unit
mechanical energy	Em	J
gravitational and/or elastic potential energy	Ep	J
translational kinetic energy	Ek	J

 

One of the most general principles in physics is the principle of energy conservation. The law of conservation of energy states that within an isolated system, energy cannot be created or destroyed, but it can be converted from one form to another. Therefore, the sum of all of the energies in the system remains constant.

 

A special case of this principle, the law of mechanical energy conservation, states that the energy of an isolated mechanical system is conserved. An isolated system is one in which no energy enters or leaves. In such a case, the mechanical energy is conserved, so any change in potential energy is accompanied by an equal but opposite change in kinetic energy. Is a downhill ski racer an isolated system that converts gravitational potential energy completely into kinetic energy? If not, does a downhill skier obey the law of mechanical energy conservation?

 

You will now use a simulation to investigate the law of mechanical energy conservation, and you’ll apply this to what is observed in a downhill ski race.

 

Physics 20 © 2008 Alberta Education