4.8.1.3 Orbital Motion, Natural and Artificial Satellites

Question 1

What does gravity provide?

Answer 1

gravity provides the force that allows planes and satellites (natural and artificial) to maintain their circular orbits

Question 2

What holds planets in orbit around the Sun?

Answer 2

• planets orbit the sun
• the force of gravity acting between the Sun and dif. planets holds the planet in its orbit

Question 3

What is the moon?

Answer 3

• natural satellite
• force of gravity holds moons in their orbits around planets

Question 4

In circular orbits what does the force of gravity lead to?

Answer 4

• force of gravity holds objects in their orbits
• in circular orbits the force of gravity is leading to change in velocity but unchanged speed
• as velocity is the speed of an object in a given direction - direction is constantly changing to velocity is contantly changing, but speed is constant - so accelerating

Question 5

How are the radius of an orbit and speed linked together for a stable orbit?

Answer 5

• if speed of a satellite increases then the radius of its orbit decreases → as at a higher speed the satellite needs a greater force of gravity to prevent it from flying off into space
  
  • so by moving closes to the Earth the gravitational force on the satellite is greater and the satellite remains in a stable orbit
• if speed of satellite decreases then radius of its orbit increases → lower force of gravitational attraction between Earth and satellite to move at slower speed

Question 6

Why does the velocity of a satellite change as it orbits earth?

Answer 6

• force of gravity causes satellite to accelerate towards earth
• acceleration causes change in direction
• velocity changes as direction changes

Question 7

Centripetal force:

Answer 7

force acting towards the centre is a resultant force