A body is thrown vertically upwards with an initial velocity of 19.6 m/s. If accelaration due to gravity $g = 9.8 m / s^{2}$ . Calculate the following:
(i) The maximum height attained by the body.
(ii) The time to reach the ground. [5 MARKS]

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Solution

Maximum height : 2.5 Marks
Total time : 2.5 Marks

(i) Given
$u = 19.6 m / s, g = - 9.8 m / s^{2}, v = 0$
$U s i n g e q u a t i o n v^{2} = u^{2} + 2 a s, w e g e t$
$0 = {19.6}^{2} + (2 \times (- 9.8) \times h)$
$h = 19.6 m$

(ii) Time taken to reach the maximum height can be calculated by the equation,
$v = u + g t$
$0 = 19.6 + (- 9.8 \times t)$
t = 2 s
In the same time, it will come back to its original position.
Total time = $2 \times 2 = 4 s$

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