Speed of Sinking
Name: Rebecca M.
What factors or variables do you need to know, to know
the speed of sinking?
This is a difficult question to answer because the "speed" at which a body
sinks depends upon its shape. For example, a ball bearing sinks very fast,
but a "boat" of the same mass may well float (like ships do). The medium on
which the body is placed. For example, a feather will float on water but not
very well on air. The Archimedian principle is that an object experiences a
buoyant force equal to the mass of the fluid displaced.
Are you referring the speed at which you sink in water -- or how fast a
For both situations: One would need to know if the water was fresh, like
that in a lake, or salty like that in the ocean or Dead Sea. The more
salt dissolved in the water, the easier it is for things to float.
For you: We would need to know your flotation potential -- are you fat or
skinny? Fat people are more buoyant and can sometimes float without
treading water -- skinny folks will sink if they do not swim or tread
For a boat: One would need to know the buoyancy of the boat materials.
Some foam boats will still float even if they have a hole in them.
Assuming we're talking about a boat that wouldn't float if it had a hole
in it, one would need to know the number and size of the holes in the
boat as well as the weight of the boat and all its contents. You would
also want to know whether or not the boat was sinking in calm waters so
that all water entered through the hole/s and did not splash in over the
Click here to return to the Physics Archives
Update: June 2012