Cam Calculations

I looked at the exam question, and I don't think it stands alone very well. First, none of the dimensions are given, nor even labeled so that you can insert your own dimensions. Maybe there was some other classroom material that was supposed to be known, but not included in the question. Further, the "black box" shown in the question was way larger than the space inside the pen, which could allow for a wildly different geometry. Depending on how much sliding there is before the mechanism slides or rolls to the next position, the pressure angle could theoretically be anything greater than zero, but a reasonable value might be around 10° or so.