Topic 8

• What shape do planets move in around the Sun?

  Elliptical orbits
• What is an ellipse?

  An oval shape with two foci
• Where is the Sun located in an ellipse?

  At one of the foci
• How does the speed of planets change relative to their distance from the Sun?

  They move faster when nearer to the Sun
• What is perihelion?

  The point where a planet is closest to the Sun
• What is aphelion?

  The point where a planet is farthest from the Sun
• What does the line connecting the Sun and a planet do?

  It sweeps out equal areas in equal times
• What is the relationship between the square of the period and the cube of the radius?

  T² ∝ r³
• What is Newton's Law of Gravitation more accurate than?

  Kepler's laws
• Why is Newton's Law of Gravitation more accurate?

  It considers the mass of both bodies
• What is the formula for gravitational force?

  F = GMm / r²
• What does the inverse square law describe?

  The relationship between gravitational force and distance