Joseph West's paper1 in the March 2014 issue of AJP is a fascinating comparison of discs with various absorption properties being slowed by photon drag. The author notes that the least realistic of the models (the no-emitting disc) is pedagogically appealing because it has the most transparent analytic structure, while both it and the emitting disc appear to have the same range within numerical round-off error, a cool result to be sure. The purpose of this letter is to note that the range of the latter disc can also be obtained analytically by direct integration, perhaps improving the classroom usage of a model like this even more. For example, the left-hand side of Eq. (11) can be written in the usual way using the chain rule as

dβEDdt=dβEDdxdxdt=cβED...
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