Chapter 3 - Think and Explain - Page 55: 65

10 m/s decrease each second while rising straight up. 10 m/s increase each second while dropping straight down. The times are the same.

Work Step by Step

This is discussed on pages 46-47. Whether it is rising or falling, the acceleration of a freely falling object, in the absence of air resistance, is always $10 \frac{m}{s^{2}}$ directed downward. Each second while going straight up, the baseball's speed decreases by 10 m/s. Each second while dropping straight down, the baseball's speed increases by 10 m/s. With no air resistance, the time going up equals the time coming down.

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