## College Physics (7th Edition)

The launch angle of the golf ball was $45^{\circ}$.
For a ball launched moving up at an angle $\theta$ to the horizontal, it also lands moving down at an angle $\theta$ to the horizontal (in Figure 3.11). The rotation of the velocity vector is thus given by the sum of the two angles above - $2\theta=90^{\circ}$. Therefore, the launch angle, $\theta$ of the golf ball was $45^{\circ}$.