8bMotion in the universe

Syllabus objectives

• 8.2know that: • the universe is a large collection of billions of galaxies • a galaxy is a large collection of billions of stars • our solar system is in the Milky Way galaxy
• 8.3understand why gravitational field strength, g, varies and know that it is different on other planets and the Moon from that on the Earth
• 8.4explain that gravitational force: • causes moons to orbit planets • causes the planets to orbit the Sun • causes artificial satellites to orbit the Earth • causes comets to orbit the Sun
• 8.5describe the differences in the orbits of comets, moons and planets
• 8.6use the relationship between orbital speed, orbital radius and time period: orbital radiusorbital speed time period 2× π ×= T rv ××= π2