WAEC - Further Mathematics (2010 - No. 32)
A stone is thrown vertically upwards and its height at any time t seconds is \(h = 45t - 9t^{2}\). Find the maximum height reached.
45. 25 m
45.50 m
56.00 m
56.25 m
Explicació
\(h = 45t - 9t^{2}\)
\(\frac{\mathrm d h}{\mathrm d t} = 45 - 18t = 0\)
\(45 = 18t \implies t = 2.5 s\)
\(h(2.5) = 45(2.5) - 9(2.5)^{2} = 112.5 - 56.25\)
= \(56.25 m.\)