What is the precise weight in ounces or grams?

Question

the precise weight in ounces or grams that it would take an object to float middepth in a body of water? trying to do a science experiment with a capsule and tank of water thanks

Answer 1

If the object is a sphere of uniform density, and it is floating halfway down in fresh water, then you can calculate the DENSITY of the object.  You cannot calculate both the size and weight. If you know the size you can calculate the weight.

To demonstrate this, if you built a sphere of wood of the correct density and it floated half way down, you could build a sphere twice as big, and it would still float halfway down.

To calculate the density, the boyancy of the part below the surface has to equal the weight of the part above the surface.  Or calculate the displacement force from the part under water, which is the weight of the displaced water, and that has to equal the total weight of the object.

If I have time later, I'll do more of the displacement calculation.

edit

V of sphere  = 4/3 πr³  r = radius in meters

V of half a sphere = 4/6 πr³

Displacement of a half sphere of water, ie, it's weight

Volume = 4/6 πr³

density of water = 1000 kg/m³

weight of water =  V x densityWater = 4/6 πr³ x 1000 in kg

so the sphere has to weigh this much to balance the displacement force.

Weight of sphere = V x density = 4/3 πr³ x density

Set the 2 equal to each other

4/3 πr³ x density = 4/6 πr³ x 1000

4/3 density = 1000 x 4/6

density = 500 kg/m³

so the density of the material has to be half that of water.

There are many woods that meet this number, although wood varies from sample to sample.

Answer 2

That is impossible to answer without more information. The weight of the object and it's configuration both affect whether it floats or not. Also is this fresh water or salt water? Salt water will support more weight than fresh water.