# P5- Sparks

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• Created by: Lauren
• Created on: 10-03-13 13:03

Satellites and Gravity

A satellite is an objecct that orbits a planet in space. Satellites can be:

-natural, for example the moon.

-artificial- they have been put in space by humans.

A satellite is kept in orbit by a gravitational force. Gravity is a universal force of attraction between masses.Gravity keeps:

-planets orbitting the Sun

-the Moon orbitting the Earth

Centripetal force acts towards the centre of a circle; it keeps an object moving in a circle. Gravity provides the centripetal force that keep a satellite in orbit.

The weight of an object depends on the gravitational force on the surface of the planet.

Weight (N)= Mass (kg) x Gravitational field strength (N/kg)

w         =       m        x          g

On Earth, gravitational field strengt, g=10N/kg

The gravitational force between 2 objects gets weaker as the object are moved further apart. If distance is doubled, the force drops to 1/4. This is called the inverse square law.

Therefore, planets very close to the Sun experience a high gravitational force compared to plants that are further away.

The difference in gravitational force means that:

-planet closer to the Sun travel very quickly and have short…