9478 / 2027

Chapter 7

Circular Motion

Separate the direction of motion from the direction of acceleration, then choose the actual forces and the correct radius.

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  1. Describe a turn

    Use radians, period and frequency to connect angular and tangential speeds, and measure repeated turns.

  2. Why acceleration points inward

    Construct a change of velocity and distinguish a finite-interval average from instantaneous inward acceleration.

  3. Choose the radial force

    Resolve actual forces in a tether and conical pendulum, and interpret force-speed data.

Syllabus coverage

This chapter covers Circular Motion, topic 7(a-f), in the 9478 syllabus (2027).

Connect angular and linear quantities to a force model, with each equation tied to its conditions.

Radians, angular velocity, inward acceleration and radial force, including horizontal-tether and conical-pendulum models.

View the learning outcomes
7(a)
Express angular displacement in radians. Describe a turn
7(b)
Understand and use angular velocity. Describe a turn
7(c)
Recall and use v = r omega. Describe a turn
7(d)
Explain centripetal acceleration in uniform circular motion, with a resultant perpendicular to the motion and towards the centre of its curved arc. Why acceleration points inward
7(e)
Recall and use a = r omega^2 and a = v^2/r. Why acceleration points inward
7(f)
Recall and use F = mr omega^2 and F = mv^2/r for the inward resultant. Choose the radial force