Advanced MathHardInterpreting a quadratic model's intercept
Advanced Math practice question
The height h, in metres, of a stone t seconds after it is thrown from a bridge is modelled by h(t) = −5t² + 10t + 15. Which statement is the best interpretation of the number 15?
- A. The stone is thrown from a height of 15 metres.Correct
- B. The stone lands after 15 seconds.
- C. The stone rises 15 metres above the bridge.
- D. The stone's speed is 15 metres per second.
Answer: A. The stone is thrown from a height of 15 metres.
h(0) = 15: the height at the moment of release.
Why the other answers are wrong
- B. The stone lands after 15 seconds.
- Landing is when h = 0, at t = 3.
- C. The stone rises 15 metres above the bridge.
- The maximum is h(1) = 20, so it rises 5 metres above the bridge.
- D. The stone's speed is 15 metres per second.
- The initial upward speed is 10.
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