(a) The graphic on the right shows an enlarged view of the piston and crank mechanism from the engine of a remote control car - Leaving Cert DCG - Question C-4 - 2011

Using a compass, draw a circle centered at point O with a radius equal to the length of crank OA. This circle represents the path traced by point A as the crank rotates.

Divide the drawn circle into 8 equal sections (each representing 45°) to facilitate understanding of the crank's position throughout one complete revolution.

For each of the angles marked on the circle, draw the position of arm AC. Mark where it intersects the vertical line through O, ensuring the extension from A to C is consistent with the angle at OA.

Identify and mark the corresponding position of point B for each position of arm AC. For each angle of rotation of the crank, trace the vertical location of point B with respect to the circular path marked.

Connect all marked points of B with a smooth curve to represent the locus of point B as the crank OA completes one full revolution. This should visually show how point B moves through space.

Indicate that from 0° to 150°, the piston rises uniformly by 60mm. Mark this segment on the displacement diagram with a straight line showing the gradual increase in height.

For the segment from 150° to 180°, represent the dwell period where piston height remains constant. Draw a horizontal line at the level reached (60mm) from the previous segment.

Illustrate the fall from 180° to 360°. Since the fall is stated to be uniform acceleration and retardation, sketch a sloping line that descends from the height of 60mm back to the original position (0mm) smoothly, ensuring the curve reflects the changing rate of displacement.

Combine all segments (rise, dwell, and fall) into one unified displacement diagram. Make sure the graph is clear, labeled appropriately, and that it reflects the motion of the piston through its complete cycle.