Isaac Newton discovered Gravity. He said that the force of gravity between two objects is: Is an attractive force Gets bigger with the mass of each object Gets smaller with greater distance between the two objects
Gravitational field strength on Earth is 10N/Kg, so the force of gravity on a person on the surface of the Earth is 500N is they are 50Kg. The Moons is 1.6N/Kg so what is the force acting on the person on the moon?
The reason is because the Earths mass is much greater and therefore it exerts a greater force on the person, compared to the Moon.
The Moon orbits us and we orbit the Sun. Elliptical circle (slightly squashed)
A planet will orbit an object that is far larger than itself To stay in orbit the object must be travelling at a particular speed orbiting around the sun What would happen if it is travelling to slow or too fast?
Geostationary and Polar satellites (man made satellites)
There are communication satellites which orbit the Earth at a particular height above the equator so that they have a period of 24 hours, and because they travel at the same speed as the Earth spins on its axis, the satellite remains above the same place of the Earth’s surface constantly.
Monitoring satellites fitted with TV cameras pointing at the Earth. For these we have many uses, including weather forecasting, police and military surveillance and environmental observations. These are much lower orbits – purely so that we can see as much detail of the Earth as possible. One period of these satellites takes between two or three hours, and their orbits go past both the Poles, so they monitor the entire Earth all day long.