What you’ll learn5 learning objectivesChoose one objective for a focused lesson, or study the complete topic.—D.1.1—Kepler’s three laws of orbital motion• Kepler’s three laws of orbital motion.Syllabus objective—D.1.2—Universal gravitation• Universal gravitation: F=Gm1m2/r^2 for point masses.Syllabus objective—D.1.3—Point-mass approximation• Extended bodies can be treated as point masses only under suitable conditions.Syllabus objective—D.1.4—Gravitational field strength• Gravitational field strength: g=F/m=GM/r^2.Syllabus objective—D.1.5—Gravitational field lines• Gravitational field lines.Syllabus objective