Weight / Gravity / Energy / Work

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:

• 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)

Kinetic Energy is motion / movement energy. Other forms of energy are heat, light, sound, electrical, and nuclear.

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)

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