Circular Motion — A/L Physics

What must I remember about Circular Motion?

• Angular Kinematics: Angular displacement θ (rad), Angular velocity ω = dθ/dt (rad/s), Angular acceleration α = dω/dt (rad/s²); Linear-angular relations: v = rω, a_tangential = rα.
• Centripetal Acceleration: Acceleration directed radially inward toward center: a_c = v²/r = rω² = vω.
• Centripetal Force: Inward net force required to sustain circular motion: F_c = m a_c = (m v²)/r = m r ω²; centripetal force is NOT a new distinct physical force, but a role played by real forces (tension, gravity, friction, normal reaction).
• Banking of Roads: Without friction: tan θ = v² / (rg); with lateral friction coefficient μ: v_max = √[ r g (tan θ + μ) / (1 - μ tan θ) ].

Test yourself (1 minute)

1. Vertical Circular Motion (mass on light string of length L)

   Critical speed at highest point to prevent slack (T ≥ 0): v_top = √(gL); Minimum speed at lowest point to complete vertical circle: v_bottom = √(5gL); Tension difference: T_bottom - T_top = 6mg.

2. Centrifugal Force in Non-Inertial Frames

   A fictitious inertial force directed radially outward: F_inertial = m ω² r, introduced ONLY when solving problems in a rotating frame of reference.

3. Conical Pendulum

   Tension T = mg / cos θ; Period of revolution T_period = 2π √(h/g) = 2π √((L cos θ)/g).

Practise Circular Motion questions today

Source: NIE G.C.E. (A/L) Physics Resource Book - Unit 2: Mechanics

What should I study first?

What comes next?

Next in the syllabus

Where does Circular Motion fit in the syllabus?

Unit 2.5 · Year 1 · Term 1