Chapter 4, Problem 36EAP

How Does the Table Know? Thinking deeply about seemingly simple observations sometimes reveals underlying truths that we might otherwise miss. For example, think about holding a golf ball in one hand and a bowling ball in the other. To keep them motionless, you must actively adjust the tension in your arm muscles so that each arm exerts a different upward force that exactly balances the weight of each ball. New, think about what happens when you set the balls on a table. Somehow, the table exerts exactly the right amount of upward force to keep the balls motionless, even though their weights are very different. How does a table know” to make the same type of adjustment that you make consciously when you hold the balls motionless in your hands? (Hint: Think about the origin of the force pushing upward on the objects.)