Mathematics

Mathematics

Problem

A ball is dropped from a height of 2 m2\,\text{m}. After each bounce it rises to 60%60\% of the height from which it fell. Ignoring the radius of the ball, calculate the total vertical distance it travels before coming to rest. a) 6.5 m6.5\,\text{m} b) 8 m8\,\text{m} c) 5 m5\,\text{m} d) 10 m10\,\text{m}
Intuitive explanation

The key insight is to split the ball's journey into two parts: the initial drop, and then an infinite series of bounces. Each bounce goes up to 60% of the previous height, then falls back down that same distance—so you're summing both ascents and descents. This is a geometric series problem in disguise: once you recognize the pattern of heights, you can use the formula for an infinite geometric sum to find the total distance without adding infinitely many terms.

Intuitive explanation

The key insight is to split the ball's journey into two parts: the initial drop, and then an infinite series of bounces. Each bounce goes up to 60% of the previous height, then falls back down that same distance—so you're summing both ascents and descents. This is a geometric series problem in disguise: once you recognize the pattern of heights, you can use the formula for an infinite geometric sum to find the total distance without adding infinitely many terms.

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