A student compiles orbital data for planets in circular orbits around a stable star. The student plots a graph with the quantity y y\,y on the vertical axis against r−1r^{-1}r−1 on the horizontal axis, where r r\,r is the orbital radius of a planet.
Only two data points are shown on the graph below.
Which quantity is represented by y y\,y on the vertical axis?
The centripetal acceleration, aca_{\text{c}}ac
The orbital speed, vvv
The square of the orbital speed, v2v^2v2
The orbital period, TTT