Chapter 14, Problem 40CRE

To determine

To explain:That the area swept out by the radial vector at time tis ,$A(t)=\frac{1}{2}\parallel r_0\times v_0\parallel t$ and thus Kepler’s Second Law continues to hold (the rate is constant) if a planet has zero mass (m = 0), then Newton’s laws of motion reduce to $r\text{'}\text{'}(t)=0$ and the orbit is a straight line.