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:

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)_