Example

Finding the Fall Time for Sunglasses Dropped from 400 Feet

Problem: Sunglasses are dropped from a bridge 400 feet above a river. Using the falling objects formula t=h4t = \frac{\sqrt{h}}{4}, find the number of seconds it takes for the sunglasses to reach the river.

  1. Read the problem.
  2. Identify: The time for the sunglasses to reach the river.
  3. Name: Let tt = time in seconds.
  4. Translate: Write the falling objects formula and substitute h=400h = 400:

t=4004t = \frac{\sqrt{400}}{4}

  1. Solve: Evaluate the square root: 400=20\sqrt{400} = 20. Then divide:

t=204=5t = \frac{20}{4} = 5

  1. Check: Substitute back: 4004=204=5\frac{\sqrt{400}}{4} = \frac{20}{4} = 5, and 5=55 = 5 is true. Five seconds is a reasonable time for a small object to fall 400 feet. ✓
  2. Answer: It takes 5 seconds for the sunglasses to reach the river.

This problem applies the seven-step formula-based strategy to the falling objects formula. Because 400400 is a perfect square (202=40020^2 = 400), the square root simplifies to a whole number, making the arithmetic straightforward.

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Updated 2026-04-21

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