Halliday, Resnick & Walker — Kinetic Energy and Work: Problem 4

4 A force \(\vec{F}_a\) is applied to a bead as the bead is moved along a straight wire through displacement \(+5.0 \text{ cm}\). The magnitude of \(\vec{F}_a\) is set at a certain value, but the angle \(\phi\) between \(\vec{F}_a\) and the bead's displacement can be chosen. Figure 7-16 gives the work \(W\) done by \(\vec{F}_a\) on the bead for a range of \(\phi\) values; \(W_0 = 25 \text{ J}\). How much work is done by \(\vec{F}_a\) if \(\phi\) is (a) \(64^\circ\) and (b) \(147^\circ\)?