Define the radian.
A circular metal disc spins horizontally about a vertical axis, as shown in the figure below (not drawn to scale).
A piece of modelling clay is attached to the disc. For the instant when the piece of modelling clay is in the position shown, draw on the figure:
an arrow, labelled V, showing the direction of the velocity of the modelling clay
an arrow, labelled A, showing the direction of the acceleration of the modelling clay.
