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03/11/2021 12:23 pm
Topic starter
A stone is dropped from a height of 20 m.
(i) How long will it take to reach the ground?
(ii) What will be its speed when it hits the ground? (g = 10 m/s2)
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03/11/2021 12:31 pm
Height, s = 20 m
Initial velocity, u = 0
Acceleration due to gravity, g = 10 m/s2
Final velocity, v = ?
Time taken, t = ?
(i) Using relation,
s = \(ut + \frac{1}{2}gt^2\)
20 = 0 x t + \(\frac{1}{2} \times 10 \times t^2\)
20 = 0 + 5t2
t2 = \(\frac{20}{5}\) = 4
t = \(\sqrt 4\) = 2s
(ii) For a freely falling body
v2 = u2 + 2gh
= \((0)^2 + 2 \times 10 \times 20\)
So, v2 = 400
v = \(\sqrt {400}\) = 20 m/s
The speed of stone when it hits the ground will be 20 m/s
This post was modified 4 years ago by Mayank1444