Question

A stone is thrown with a velocity of 39.2ms- making 30° with the horizontal. The time after which
it is at a height of 14.7 m is​

Answer 1

Answer:

S = (v0sin30°)t - 1/2gt²

14.7 = (39.2 x 1/2) t - 1/2 x 9.8 x t²

14.7 = 19.6t - 4.9t²

4.9t² - 19.6t + 14.7 = 0

4.9t² - 14.7t - 4.9t + 14.7 = 0

4.9t (t - 3) - 4.9 (t - 3) = 0

(4.9t - 4.9)(t-3) = 0

so t can be 1 or 3sec

Explanation:

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Answer 2

s = (v0sin30°)t - 1/2gt²

14.7 = (39.2 x 1/2) t - 1/2 x 9.8 x t²

14.7 = 19.6t - 4.9t²

4.9t² - 19.6t + 14.7 = 0

4.9t² - 14.7t - 4.9t + 14.7 = 0

4.9t (t - 3) - 4.9 (t - 3) = 0

(4.9t - 4.9)(t-3) = 0

so t can be 1 or 3sec