Motion in the universe

Question 1

What is the universe?

Answer 1

• The universe is a large collection of billions of galaxies.

Question 2

What is a galaxy?

Answer 2

• A galaxy is a large collection of billions of stars held together by gravity.
• Example: The Milky Way is our galaxy.

Question 3

Where is our solar system located?

Answer 3

• Our solar system is located in the Milky Way galaxy.

Question 4

Why does gravitational field strength, g, vary on different planets and moons?

Answer 4

• Gravitational field strength (g) depends on:
  
  • The mass of the planet or moon (larger mass = stronger gravity).
  • The radius of the planet or moon (larger radius = weaker gravity at the surface).
• Example:
  
  • The Moon has weaker gravity than Earth due to its smaller mass.
  • Jupiter has stronger gravity than Earth due to its much larger mass.

Question 5

What does gravitational force cause?

Answer 5

• Gravitational force causes:
  
  • Moons to orbit planets (e.g., the Moon orbits Earth).
  • Planets to orbit the Sun (e.g., Earth orbits the Sun in an elliptical path).
  • Artificial satellites to orbit Earth (e.g., GPS and weather satellites).
  • Comets to orbit the Sun in long elliptical orbits.

Question 6

What are the differences in the orbits of comets, moons, and planets?

Answer 6

• Planets: Nearly circular orbits around the Sun.
• Moons: Nearly circular orbits around planets.
• Comets: Highly elliptical orbits around the Sun, spending most of their time far from it.
• Comets speed up as they get closer to the Sun due to stronger gravitational pull.
• Artificial satellites: Can have circular or elliptical orbits around Earth.

Question 7

What is the equation for orbital speed?

Answer 7

• The relationship between orbital speed (v), orbital radius (r), and time period (T) is:
  v = (2πr) / T
  Where:
  
  • v = orbital speed (m/s)
  • r = orbital radius (m)
  • T = time period (s)
• This equation helps calculate how fast a planet, moon, or satellite moves in its orbit.