Chapter 4, Problem 87GP

Projectiles: Coming or Going? Most projectiles continually move farther from the origin during their flight, but this is not the case if the launch angle is greater than ${\cos }^{-1}\left(\frac{1}{3}\right)$ = 70.5°. For example, the projectile shown in Figure 4-34 has a launch angle of 75.0° and an initial speed of 10.1 m/s. During the portion of its motion shown in red, it is moving closer to the origin—it is moving away on the blue portions. Calculate the distance from the origin to the projectile (a) at the start of the red portion, (b) at the end of the red portion, and (c) just before the projectile lands. Notice that the distance for part (b) is the smallest of the three.

Figure 4-34

Problem 87