# A ball is thrown horizontally from the top of a cliff and lands on the ground below. Explain why the ball's speed increases from the moment it is released until it reaches the ground, and state the name given to the constant speed that a falling object can reach when passing through air.

> Cambridge International IGCSE Physics (0625) — 1.2 Motion · Explain · 4 marks

> A ball is thrown horizontally from the top of a cliff. Air resistance acts on the ball throughout its fall.

## Mark scheme (4 marks)

1. The weight (gravitational force) acts downward on the ball / gravity accelerates the ball downward
2. The resultant force is downward (because weight is greater than air resistance), causing acceleration / increasing speed
3. As speed increases, air resistance increases (but remains less than weight throughout the fall to the ground)
4. Terminal velocity — the constant speed reached when weight equals air resistance (zero resultant force / zero acceleration)

## Related

- [Revision notes for Cambridge International IGCSE Physics (0625)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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