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A stone is thrown straight up with initial velocity 20 m per second. Taking g = 10 m per second squared, the maximum height reached is:
A10 m
B15 m
C20 m
D25 m
Answer & Solution
Correct answer: C. 20 m
1. At the highest point, the upward velocity becomes zero.
2. Treat the upward direction as positive; acceleration is −g (downward) acting on the stone.
3. Use v² − u² = 2as with v = 0, u = 20, a = −10.
4. So 0 − 400 = 2 × (−10) × s.
5. s = 400 / 20 = 20 m.
6. Hence the stone rises to a maximum height of 20 m.
_Source: Selina Concise Physics ICSE Class 9, Ch 2 'Motion in One Dimension' (aplustopper.com extract)_
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