What you’ll learn12 learning objectivesChoose one objective for a focused lesson, or study the complete topic.—A.4.1 (HL)—Torque• Torque about an axis: τ = Fr sin θ.Syllabus objective—A.4.2 (HL)—Rotational equilibrium• Bodies in rotational equilibrium have a resultant torque of zero.Syllabus objective—A.4.3 (HL)—Unbalanced torque• An unbalanced torque applied to an extended, rigid body will cause angular acceleration.Syllabus objective—A.4.4 (HL)—Angular motion quantities• The rotation of a body can be described: angular displacement, angular velocity and angular acceleration.Syllabus objective—A.4.5 (HL)—Angular motion equations• Use rotational SUVAT equations under uniform angular acceleration.• Variables include θ/Δθ, angular speed ω and angular acceleration α.Syllabus objective—A.4.6 (HL)—Moment of inertia• Moment of inertia depends on mass distribution about the rotation axis.Syllabus objective—A.4.7 (HL)—Point-mass moment of inertia• Point-mass moment of inertia: I = Σmr^2.Syllabus objective—A.4.8 (HL)—Rotational Newton’s second law• Rotational Newton’s second law: τ = Iα.Syllabus objective—A.4.9 (HL)—Angular momentum• Angular momentum of a rotating body: L = Iω.Syllabus objective—A.4.10 (HL)—Angular momentum conservation• Angular momentum remains constant unless the body is acted upon by a resultant torque.Syllabus objective—A.4.11 (HL)—Angular impulse• Angular impulse changes angular momentum: ΔL = τΔt = Δ(Iω).Syllabus objective—A.4.12 (HL)—Rotational kinetic energy• Rotational kinetic energy: Ek = 1/2Iω^2 = L^2/2I.Syllabus objective