Physics Form 4: Chapter 2 - Principle of Conservation of Energy

• The principle of conservation of energy shows that energy cannot be created or destroyed but can change from one form to another.
• The principle of conservation of energy states that the total quantity of energy in an enclosed system is always the same.
  

For example:  Energy transformation on a roller coaster

• At the top of the hill, the cars possess the maximum quantity of potential energy. Potential energy  is dependent upon the mass of the object and the height of the object. The car's large quantity of potential energy is due to the fact that they are elevated to a large height above the ground. 

• As the cars descend the first drop, they lose much of this potential energy in accord with their loss of height. The cars subsequently gain kinetic energy. Kinetic energy is dependent upon the mass of the object and the speed of the object. 

• The train of coaster cars speeds up as they lose height. Thus, their original potential energy (due to their large height) is transformed into kinetic energy (revealed by their high speeds). As the ride continues, the train of cars are continuously losing and gaining height. 

• Each gain in height corresponds to the loss of speed as kinetic energy (due to speed) is transformed into potential energy (due to height). Each loss in height corresponds to a gain of speed as potential energy (due to height) is transformed into kinetic energy (due to speed).

Conclusion:

1. Potential energy convert to kinetic energy and vice versa
2. Total energy in the system is still the same.