# A cube is placed in a pool of water. If the cube is 38 cm long on each side,?

what is the weight of the cube? (Use 1000 kg/m3 for the density of water)

I got the answer 537745600 but it was graded as wrong, can you please explain how to do this question in detail?

### 6 Answers

- TomLv 74 months ago
HOW far into the water does it sink?-----EVEREYTHING put in water will sink until it displaces it's own weight in water and then it will stop sinking---You find the volume of water the cube pushed aside as it is floating.(how much of the cube is beneath the surface) Each cc is one gram. If the cube sinks completely, that means it cannot displace enough weight in water volume to hold it up---it is denser than water.---It will still weigh LESS under water, by the weight of water it pushes aside, but it will still sink to the bottom-------Since you are not told HOW much of the cube is submerged, there is no way to figure its weight.-----

- NCSLv 74 months ago
If your cube is submerged, there is no way to know its weight using the supplied data.

If your cube is floating with height "h" above the surface of the water, then its weight is

W = (h/38cm)*(38cm)³*0.001kg/cm³*9.8m/s²

or W = 14.15h

for h in cm and W in newtons.

You appear to have done 38³ * 1000 * 9.8

which is dimensionally inconsistent (mixing cm³ and m³) and fails to consider that only part of the cube is submerged.

Hope this helps!

- MorningfoxLv 74 months ago
How did you get 537745600? Why so many digits, way more than significant? And isn't weight measured in newtons? Or sometimes in kilogram-equivalent?

- JohnLv 44 months ago
Your not going to know the weight of the cube without knowing amount of water displaced. You need more than cube measurement. Plus there is this. You can have the same amount of water displaced by different cubes.

Because really you need to know the RATE the water was displaced because the different types of cubes displace water at different rates.

And that s the real measure in using liqyid to find weight.

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- Anonymous4 months ago
A cube of what?

< I got the answer 537745600 but it was graded as wrong >

Does that look reasonable to you? Remember anything about including units?

- billrussell42Lv 74 months ago
you are not listing the entire problem, as this is not answerable as is.

The cube could be anything from steel to styrofoam, and each would have a different weight.

BTW, if the cube is submerged, we know it weights AT LEAST (0.38m)³*9.8m/s²*1000kg/m³ = 538 N