Gravitational Field & Speed of Light
Physics: Cambridge International GCSE Supplement, topic 6.1.4
Gravitational Field & Speed of Light
A gravitational field is the region around a mass where another mass feels a force of attraction.
Strength of gravity
- The strength of gravity at a planet’s surface depends on the planet’s mass.
- The bigger the mass, the stronger the gravity at the surface.
- The strength of gravity decreases the further you move away from the planet.
Light speed
- Light travels at a speed of about 3 × 108 m/s.
- To find the time light takes to travel, we use this formula:
- This lets us calculate light travel times between the Sun, Earth, and other objects in the Solar System.
- For example, the distance from the Sun to the Earth is 1.5 × 1011 m, so it takes about 8 minutes for the light to travel from one to the other.
Test yourself on Gravitational Field & Speed of Light
Which factor mainly determines the strength of gravity at a planet’s surface?
What happens to the gravitational field strength as the distance from a planet increases?
At its closest, Mars is about 5.6 × 1010 m. Using the speed of light as 3 × 108 m/s, calculate how long it takes for light to travel this distance.
The distance from Earth to the Moon is about 3.8 × 108 m. Using the speed of light as 3 × 108 m/s, calculate how long it takes for light to travel this distance.