Question: Moving objects left the traces labeled A-F in Figure 1.54. The dots were deposited at equal time intervals (for example, one dot each second). In each case the object starts from the square. Which trajectories show evidence that the moving object was interacting with another object somewhere? If there is evidence of an interaction, what is the evidence?

The path taken by a mass in motion through space as a function of time is known as a trajectory, sometimes known as a flight path. The term "trajectories" is frequently used to describe the type of motion that an object is enduring.

$\left(A\right)$In this case, there is no interaction because the object is moving in a straight line with constant velocity.

$\left(B\right)$The object is changing its speed with time since the distance between the dots is increasing. So, there is some interaction.

$\left(C\right)$The object has changed its direction. It means that its velocity is not constant. So, some interaction must be present.

$\left(D\right)$The object is moving in a circular path of concentric circles. Hence, its velocity is changing every second. There, must be some interaction.

$\left(E\right)$The object is moving in a circular path. Hence, its velocity is changing every second. There, must be some interaction.

$\left(F\right)$The object is moving in a circular path. Hence, its velocity is changing every second. There, must be some interaction.

Thus, out of all, the trajectories (B), (C), (D), (E) and (F) show evidence that there was significant interaction.