Question

A stone falls from a train trestle. The stone's height in meters above the ground is modeled by the function h(t)=−4.9t2+155 where t is time in seconds. To the nearest tenth of a second, how long does it take the stone to hit the ground? State what strategy you will use to answer the question, and then find the answer.

Answer 1

5.6s

Explanation:

Given the height reached by the stone modeled by the equation

h(t)=−4.9t2+155 where t is time in seconds.

The stone hits the ground at h(t) = 0

Substitute

0 = -4.9t²+155

4.9t² = 155

t² = 155/4.9

t² = 31.63

t = ±√31.63

t = 5.62seconds

Hence it will take 5.6s to reach the ground(to the nearest tenth)