orbital motion & satellites

Question 1

how can planets maintain orbit?

Answer 1

the force of gravity

Question 2

describe the similarities and distinctions between the planets, their moons, and artificial satellites

Answer 2

similarities-
- all orbit around a larger object (planets - sun), (moons + satellites - their planet)
- all move, and are influenced by gravity

differences-
- artificial satellites are human made and built for specific purposes
- planets much bigger

Question 3

how can the force of gravity can lead to changing velocity but unchanged speed in circular objects?

Answer 3

• if an object is travelling in a circle, it is constantly changing direction
• velocity is a vector quality so has a magnitude and direction
• direction is changing so velocity is changing
• speed is a scalar quality so only has a magnitude, which is unchanging
• for an object to accelerate, a force has to be acting on it which is directed towards the centre of the circle
• the force would cause the object to fall but as it is already moving, it causes it to change direction
• the object keeps accelerating towards what its orbiting but the velocity keeps it travelling in a circle

Question 4

why must the radius change if the speed changes for a stable orbit?

Answer 4

• the closer you get to a star/planet, the stronger the gravitational force is
• the stronger the force, the faster the orbiting object needs to travel to remain in orbit
• so if the speed of an object changes, the radius of its orbit must change, as it would crash into the object otherwise