GCSE Physics Unit 3 Revision (4)

Gravity and Planetary Orbits

• Gravity is the centripetal force that keeps planets in orbit
• Gravity is the force of attraction between masses - the larger the masses the greater the forces of gravity between them.
• The gravitational force acts as the centripetal force which keeps one object orbiting another. 
• An orbit is possible when there is a balance between the motion of the object and the gravity pulling it inwards.
• Planets orbit stars in elliptical (slightly squashed) circles. 
• The further the planet is from the Sun, the longer it takes…