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Why is an anchor heavy enough to stop a ship,but not sink it while it's on board?
- Lily (age 9)
Woodstock, GA, USA
The anchor is involved in two forces:
1. gravity- it's heavy
2. A sort of friction- it gets stuck in the sea floor.
To keep the ship from blowing away, you need that sideways force (2) to be stronger than any sideways force from the wind or from water currents.
To keep the ship from sinking, you need that the downward force (1) isn't bigger than the upward force from water pushing on the bottom of the ship.
There's no reason that both of these can't be true. They involve different comparisons.
(published on 06/03/2011)
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