In Exercise 59, what are the relative velocities if the ball is thrown in the direction of the truck?
Exercise 59
A person riding in the back of a pickup truck traveling at \(70 \mathrm{~km} / \mathrm{h}\) on a straight, level road throws a ball with a speed of \(15 \mathrm{~km} / \mathrm{h}\) relative to the truck in the direction opposite to the truck's motion. What is the velocity of the ball (a) relative to a stationary observer by the side of the road, and (b) relative to the driver of a car moving in the same direction as the truck at a speed of \(90 \mathrm{~km} / \mathrm{h}\) ?