Angular motion and the axes of rotation

Overview

Angular motion from an eccentric force, the diver's take-off, the longitudinal, frontal and transverse axes with sporting examples, twisting somersaults, the golfer's hips, angular velocity and radians.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   Define angular motion.

   Model answer

   Angular motion is movement of a body or part of a body in a circular path about an axis of rotation.

2. 2

   How is angular motion created?

   Model answer

   Angular motion is created by an eccentric force, whose line of action passes outside the centre of mass. The eccentric force produces a turning effect called torque.

3. 3

   How does the distance of an eccentric force from the centre of mass affect rotation?

   Model answer

   The further the line of force is from the centre of mass, the greater the turning effect. A greater turning effect produces more rotation.

4. 4

   How does a diver create rotation at take-off from the springboard?

   Model answer

   The diver leans so that the reaction force from the board passes outside the centre of mass. The resulting eccentric force starts the somersault.

5. 5

   Describe the longitudinal axis.

   Model answer

   The longitudinal axis runs vertically from head to toe. Rotation about the longitudinal axis produces twisting or spinning movements.

6. 6

   Give two sporting examples of rotation about the longitudinal axis.

   Model answer

   An ice skater spinning on the spot rotates about the longitudinal axis. A discus thrower's turn in the circle is another example.

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