Boxi Learn › Physics › Stage 3 · Structure and Evidence
How hard does water push up?
PHY-1 A force changes motion, it does not keep it goingX-1 Guess, then checkX-2 Evidence outweighs opinion
What many people think
The deeper an object sinks, the harder the water pushes it up.
The idea
The upward push equals the weight of the water the object shoves aside; once it is fully under, going deeper does not change it.
Explain it
A friend says a submarine gets pushed up harder the deeper it dives. Using the words “water pushed aside” and “volume”, explain what really happens to the push once it is fully under.
Try at home
Put a bowl of water on a kitchen scale. Hang a stone or an unopened drink can on a thread and lower it in without touching the bowl: the scale rises by as many grams as there are cm³ under water. Go deeper — does the number change?