P+M tutor summary notes

• universe is a large collection of billions of galaxies
• galaxy is a large collection of billions of stars
• a solar system is a collection of planets orbiting a common star. our solar system is the milky way galaxy
• gravitational field strength is the force per unit mass on a body in a gravitational field
• gravitational field strength is measured in newtons per kilogram n/kg
• gravitational field strength varies with the mass and size of the body and is therefore different on other planets and the moon compared to earth
• weight = mass x gravitationl field strength w=mg
• gravitational force enables the various bodies to orbit around others
• moons orbit planets - the orbits are sightly elliptical with near constant orbital speed
• planets and comets orbit the sun - the orbits of planets are slightly elliptical with near constant orbital speed. the orbits of comets are highly elliptical.
• artificial satellites orbit the earth - the greater the orbital radius or the smaller the time period = the greater the orbital speed