A student investigates the motion of a model train accelerating from rest along a straight track with constant acceleration aaa. The student records the displacement s s\,s from the starting position at various times ttt, and plots a graph of s s\,s on the vertical axis against t2 t^2\,t2 on the horizontal axis.
What physical quantity does the gradient of this straight-line graph represent?
The acceleration of the train, aaa
Half of the acceleration of the train, 12a\frac{1}{2}a21a
Twice the acceleration of the train, 2a2a2a
The average velocity of the train