85.3 the limitation to applying Newtons law of m otion The trajectory of the Cassini mission to Saturn Saturn arrival us flyby 10Ju|2004 Venus flyby 29Jun1999 米 Launch 8 Jan 2000 15oct1997 Earth flyby 25Auq1999 85.4 Some topics of discussion 1. Do inertial frames really exist? Inertial reference frame is an ideal model The earth spins on its axis. The centripetal acceleration is less than 3. 4x10-2m/s2 The surface of the earth is a approximate inertial reference frame The earth moves around the sun. The centripetal acceleration is 6x10-m/s2.6 §5.3 the limitation to applying Newton’s law of motion The trajectory of the Cassini mission to Saturn 1. Do inertial frames really exist? Inertial reference frame is an ideal model. The earth spins on its axis. The centripetal acceleration is less than 3.4×10-2m/s2. The surface of the earth is a approximate inertial reference frame. The earth moves around the sun. The centripetal acceleration is 6×10-3m/s2. §5.4 Some topics of discussion