Question

While hiking, Julia kicked a small rock off a ledge that was meters above a crevasse. Graph the situation using the formula y = 4.9t^2 + 9. Use the graph to determine when the rock will hit the bottom of the crevasse, 2 meters below ground level. Round your answer to the nearest tenth of a second.

Answer 1

Take y = 11 (11 m below the ledge = 9 m to ground + 2 m below ground). Solve

4.9t^2 + 9 = 11
4.9t^2 = 2
t^2 = 2/4.9 ≈ 0.40816
t ≈ √0.40816 ≈ 0.639 s

Rounded to the nearest tenth: t ≈ 0.6 seconds.