Energy is ABILITY to do work.
Energy can be found in a number of form. they are:
1. Mechanical (kinetic and potential)
2. Electrical
3. Heat
4. Light
5. Thermal
6. Chemical
The law of conservation of energy (hukum kekekalan energi):
Energy can neither be created nor destroyed, it can only be converted from one form to another.
Example of energy conversion
1. Laptop = chemical (battery) > electric > heat + light + sound
Exercise
1. Examine energy conversion in handphone!
2. Examine energy conversion in car!
3. Examine energy conversion in our body!
How to avoid excess energy:
- Exercise regularly, because we need energy to exercise, so we can avoid excess energy.
- Control sugar consumption, because in the digestion of food will be convert into sugar.
- Consume healthy food (“real food”) and fibrous food, because it can maintain our nutrition and energy.
Application of energy in everyday life
- Work done by a machine uses mechanical energy.
- Digestion of food uses chemical energy
- Moving windmill uses kinetic energy
- Battery in electronic device uses potential energy
Work
Work is done:
(i) A force acts on the body.
(ii) There is a displacement