A stone is thrown vertically upwards and its height at any time t seconds is (h = 45t – 9t^{2}). Find the maximum height reached.
-
A.
45. 25 m -
B.
45.50 m -
C.
56.00 m -
D.
56.25 m
Correct Answer: Option D
Explanation
(h = 45t – 9t^{2})
(frac{mathrm d h}{mathrm d t} = 45 – 18t = 0)
(45 = 18t implies t = 2.5 s)
(h(2.5) = 45(2.5) – 9(2.5)^{2} = 112.5 – 56.25)
= (56.25 m.)