Weight and Gravity
The weight of an object is the force of gravity acting on it. It is calculated using the following formula:
Weight (N) = Mass (kg) x g (N/kg or m/s2)
This force of gravity is explained by considering the earth to be surrounded by a gravitational field. The strength of this field is the force acting upon a mass of 1kg and this is 9.8 N/kg near the surface.
Energy and Work
Energy exists in many different forms and can be changed from one form into another. There are 2 main types of energy:
Kinetic Energy is motion / movement energy. Other forms of energy are heat, light, sound, electrical, and nuclear.
- Potential Energy (PE) - some examples are:
Gravitational PE (GPE) - energy stored due to position (e.g. being high up)
Elastic PE - energy stored in a stretched spring
Chemical PE - energy stored in a fuel
Magnetic PE - energy stored in a magnetic field
- Kinetic Energy (KE)
Work is done when energy is changed (transferred) from one form into another. (e.g. in lifting a weight up, energy is transferred from chemical energy (in the person's muscles) to GPE)