C-4. (a) The images on the right show an enlarged view of the piston and crank mechanism from the engine of a jet ski - Leaving Cert DCG - Question C-4 - 2016

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

Divide the circle into equal segments of 30° to effectively plot the positions of points A and subsequently point B. Label each division clearly.

For each 30° increment, draw arm AC extending from point A to its endpoint B. This will illustrate how point B moves as the crank rotates.

Mark the position of point B for each angle as you progress around the circle. Utilize a ruler for accuracy in positioning point B.

Connect the plotted points B with a smooth curve to visualize the path traced by point B during the crank's rotation.

Identify and plot the follower's position for the respective angles indicated. At 0°, the follower remains at 50mm height. At 90°, it continues at the same height, then descends as follows.

During this period, the follower remains stationary, thus maintaining a height of 50mm throughout this range of motion.

The follower moves uniformly from a height of 50mm to a height of 0mm as the crank moves from 90° to 180°. This descent occurs at a steady rate.

During this motion from 180° to 360°, the follower will first accelerate downwards and then decelerate upwards, providing a smooth transition. Draw corresponding angles reflecting this acceleration and deceleration.

Finalize the displacement diagram by connecting all the plotted points and marking clear height values at the relevant 30° increments. Ensure the diagram is neat and clear for presentation.