The correlation between the hardness of a tennis ball and the distance it travels
The hypothesis that the softer ball will be bouncier and be able to travel longer distance compared to harder balls is proven to be true.
The manufacturers of sports gear use different methodologies when producing their balls. Each manufacturer has his own know how or secret formula, which is based on knowledge, research or experience. That is why although different balls look the same from the exterior, balls from different manufacturers will perform differently under different conditions. This gives sports enthusiasts the opportunity to choose the ball that best enhances their performance.
The experiment can also be done on a concrete floor instead of in a field.
Try to repeat the experiment under different temperature conditions.
Be careful not to stand in the path of trajectory of the balls when they are launched.