How to Rank Radial Acceleration Magnitudes from Angular Velocity Graph?

[keemosabi]

Homework Statement

Figure 10-22 is a graph of the angular velocity versus time for the rotating disk of Fig. 10-21a.

For a point on the disk rim, rank the instants a, b, c, and d according to the magnitude of the radial acceleration, greatest first (use only the symbols > or =, for example b=d>a>c).

Homework Equations

\alpha = d\omega/dt

The Attempt at a Solution

I figured that the angular acceleration is just the slope of the angular velocity graph, so the magnitudes from greatest to least would be c>a>b=d.

What did I do wrong? The site says that I am wrong.

 

[tiny-tim]

Hi keemosabi!

Read the question!

Figure 10-22 is a graph of the angular velocity versus time for the rotating disk …
For a point on the disk rim, rank the instants a, b, c, and d according to the magnitude of the radial acceleration …
…
I figured that the angular acceleration …

angular?