What you’ll learn26 learning objectivesChoose one objective for a focused lesson, or study the complete topic.—A.2.1—Newton’s three laws of motion• Newton’s three laws of motion.Syllabus objective—A.2.2—Forces as interactions between bodies• Forces as interactions between bodies.Syllabus objective—A.2.3—Free-body diagrams• Forces acting on a body can be represented in a free-body diagram.Syllabus objective—A.2.4—Resultant force from diagrams• Free-body diagrams can be analysed to find the resultant force on a system.Syllabus objective—A.2.5—Contact forces• Contact forces include normal, friction, tension, elastic restoring force, viscous drag and buoyancy.Syllabus objective—A.2.6—Normal force• Normal force FN acts perpendicular to the contact surface.Syllabus objective—A.2.7—Frictional force• Friction acts parallel to contact.• Static: Ff <= μsFN; dynamic: Ff = μdFN.Syllabus objective—A.2.8—Tension• Tension.Syllabus objective—A.2.9—Hooke’s law restoring force• Elastic restoring force follows Hooke’s law: FH = -kx.Syllabus objective—A.2.10—Viscous drag• Viscous drag on a small sphere: Fd = 6πηrv, opposite motion.• η is fluid viscosity, r sphere radius, v speed through fluid.Syllabus objective—A.2.11—Buoyancy• Buoyancy from displaced fluid: Fb = ρVg.Syllabus objective—A.2.12—Field forces• Know field forces: gravitational, electric and magnetic.Syllabus objective—A.2.13—Weight• Weight is gravitational force: Fg = mg.Syllabus objective—A.2.14—Electric force Fe• Electric force Fe.Syllabus objective—A.2.15—Magnetic force Fm• Magnetic force Fm.Syllabus objective—A.2.16—Linear momentum conservation• Linear momentum p=mv is conserved unless a resultant external force acts.Syllabus objective—A.2.17—Impulse• Impulse from resultant external force: J = FΔt = Δp.Syllabus objective—A.2.18—Impulse-momentum change• The applied external impulse equals the change in momentum of the system.Syllabus objective—A.2.19—Newton’s second law forms• Use F=ma for constant mass; use F=Δp/Δt when mass changes.Syllabus objective—A.2.20—Elastic and inelastic collisions• Elastic and inelastic collisions of two bodies.Syllabus objective—A.2.21—Explosions• Explosions.Syllabus objective—A.2.22—Collision energy• Compare energy in elastic collisions, inelastic collisions and explosions.Syllabus objective—A.2.23—Centripetal acceleration• Centripetal acceleration is radial: a=v^2/r=ω^2r=4π^2r/T^2.• Direction is radially toward the centre of the circle.Syllabus objective—A.2.24—Centripetal force• Circular motion is caused by a centripetal force acting perpendicular to the velocity.Syllabus objective—A.2.25—Direction change in circular motion• A centripetal force causes the body to change direction even if its magnitude of velocity may remain constant.Syllabus objective—A.2.26—Angular and linear speed• Circular motion relation: v=2πr/T=ωr.• Use angular velocity ω and period T to link angular and linear descriptions.Syllabus objective
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