Final answer:
A beach ball weighs less than a bowling ball because it has less mass, leading to a weaker gravitational attraction to Earth, and thus a lower weight.
Step-by-step explanation:
The reason a beach ball weighs less than a bowling ball is because of the difference in their mass and the resultant gravitational force that Earth exerts on them. Mass is a measure of the amount of matter in an object, and since the bowling ball is made of a dense material such as hard plastic or urethane and filled with heavy substances, it contains more matter than a beach ball, which is mainly filled with air. The gravitational force, or weight, of an object on Earth is directly proportional to its mass. Therefore, the beach ball is less strongly attracted to Earth than the bowling ball, resulting in a lower weight.