Halliday, Resnick & Walker — Motion in Two and Three Dimensions: Problem 60

60 A centripetal-acceleration addict rides in uniform circular motion with period \( T = 2.0\text{ s} \) and radius \( r = 3.50\text{ m} \). At \( t_1 \) his acceleration is \( \vec{a} = (6.00\text{ m/s}^2)\hat{i} + (-4.00\text{ m/s}^2)\hat{j} \). At that instant, what are the values of (a) \( \vec{v} \cdot \vec{a} \) and (b) \( \vec{r} \times \vec{a} \)?