Chapter 13, Problem 82P

You’re working for the summer with an ornithologist who knows you’ve studied physics. She asks you for a noninvasive way to measure birds’ masses. You propose using a bird feeder in the shape of a 50-cm-diameter disk of mass 340 g, suspended by a wire with torsional constant 5.00 N·m/rad (Fig. 13.36). Two birds land on opposite sides and the feeder goes into torsional oscillation at 2.6 Hz. Assuming the birds have the same mass, what is it?

FIGURE 13.36 Problem 82