A biker rider moving along at a constant pace can be represented by dots that are evenly spaced apart.

Dots evenly spaced apart.

The particle model for the bird would simply be four equally spaced dots. It’s best to choose the central point of the bird when you choose to make a particle model.

Four evenly spaced dots; center of the bird

As the car comes to a complete stop, the particles will become closer together as it gets closer to the stop sign. As usual, use the central point of the car to determine the position of the particles in your model.

Dots get closer together on the left.

Let’s say Runner 1 crosses the finish line after 4 minutes. The particle model would look like the image on the left.

The first runner crosses the finish line when the second runner is done with three-quarters of the race. That means that the second runner is where the first runner was at 3 minutes!

Runner 2 is represented with the red dots.