Orbit

• Gravity keeps planets, artificial satellites and moons in orbit.
• As a body orbits, its speed stays the same but its velocity changes because the direction changes.
• The further a satellite is from a planet, the slower it is and it takes longer to orbit.
• If the speed of an artificial satellite orbiting the Earth increases, the radius of its orbit decreases. This is because at a higher speed, the satellite needs a greater force of gravity to prevent it from flying off into space. By moving closer to the Earth, the gravitational force on the satellite is greater, and it stays in a stable orbit.