Final answer:
The ball travels a total distance of 40 meters (20 meters up and 20 meters down), but the displacement is zero because the ball returns to its starting point.
Step-by-step explanation:
To answer your questions, when a ball is thrown straight up to a height of 20 meters and then falls straight down to the starting point, the total distance the ball travels is 40 meters, which is the sum of the upward and downward paths. However, the displacement of the ball is zero because displacement is a vector quantity that considers the initial and final positions of the ball, which in this case are the same point.
The subject matter of this question involves concepts from kinematics, a branch of Physics, specifically the treatment of distance and displacement in one-dimensional motion.