The Sun's Gravitational Field
Physics: Cambridge International GCSE Supplement, topic 6.1.5
The Sun's Gravitational Field (cont.)
Effect on the planets
- The Sun’s gravitational field strength decreases as you move further away.
- Planets closer to the Sun move faster in their orbits.
- Planets further away move more slowly.
Orbits
- Orbits are often elliptical (oval-shaped), not perfect circles.
- An object in an elliptical orbit travels faster when closer to the Sun.
- This happens because of the conservation of energy.
Conservation of energy
- Near the Sun, the object is deeper in the gravitational field, so gravitational potential energy decreases.
- This energy changes into kinetic energy, so the object speeds up.
- Further from the Sun, the opposite happens: more potential energy, less kinetic energy, so the object slows down.
Test yourself on The Sun's Gravitational Field
Why do planets orbit the Sun and not each other?
What would happen to the planets if the Sun’s gravity suddenly disappeared?
Approximately what fraction of the Solar System’s mass is in the Sun?
Why is the Sun’s gravity so strong compared to the planets?
What happens to the strength of the Sun’s gravitational field as distance increases?