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9702 · 12.1

Kinematics of uniform circular motion — common mistakes

Common exam mistakes on 9702 Kinematics of uniform circular motion. Learn what loses marks, then practise the topic with Examiner’s Ink.

Exam tip 1

Always remember that centripetal force is a resultant force – it isn't a new type of force! It's provided by existing forces like tension, gravity, or friction. Also, ensure your angles are in radians when using angular velocity formulas.

What are the key differences between linear and angular velocity?

Linear velocity (vv) describes how fast an object is moving along its path, tangent to the circle, and its unit is m s⁻¹. Angular velocity (ω\omega) describes how fast the angle is changing from the centre, measured in radians per second (rad s⁻¹), and it applies to the rotation itself.

Can an object in uniform circular motion have zero acceleration?

No, an object in uniform circular motion is always accelerating. Even though its speed is constant, its direction of motion is continuously changing. Since velocity is a vector quantity (magnitude and direction), a change in direction means a change in velocity, which by definition is acceleration.

What provides the centripetal force in real-world examples?

The centripetal force is often provided by other familiar forces. For instance, gravity provides the centripetal force for satellites orbiting Earth, tension provides it for a ball swung on a string, and friction provides it for a car turning a corner.