Apitching machine is programmed to pitch baseballs horizontally at a speed of 83 mph . the machine is mounted on a truck and aimed backward. as the truck drives away from a man at a speed of 55 mph , the machine shoots a ball towards him.

28 mph

Explanation:

We can find the velocity of the ball relative to the player by looking at the relative motion between the machine and the man.

Assuming the truck (and the machine) is moving backward and the ball is launched in the forward direction (toward the man), we have:

is the velocity of the ball relative to the machine

is the velocity of the machine relative to the man

Therefore we can write:

where v' is the velocity of the ball relative to the man. Solving,