.
The catapulted person touches the lake when its height is zero.
Therefore, the equation to solve is THIS
-16t^2 + 50t + 20 = 0.
To solve it, simplify it first
8t^2 - 25t - 10 = 0,
then apply the quadratic formula
= = .
We deny the negative root and accept the positive root t = = 3.48 seconds (rounded).
Solved.
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To see many other similar solved problems, look into the lessons
- Introductory lesson on a projectile thrown-shot-launched vertically up
- Problem on a projectile moving vertically up and down
- Problem on an arrow shot vertically upward
- Problem on a ball thrown vertically up from the top of a tower
- Problem on a toy rocket launched vertically up from a tall platform
in this site.
Learn the entire subject from this source.