BR Physics Question: Identifying sunken object

[Bottle]

I'm having trouble understanding question 5.4b on BR Physics I book.

The question goes: What is the specific gravity of an object that weighs 36 newtons in air but only 9 newtons in water at 4C?
A. 0.25 B. 1.33 C. 3.00 D. 4.00
The answer ends up being 1.33

The solution explanation says first thing to do is to identify that the object is a sunken object rather than a floating object. How Am I supposed to distinguish between sunken and floating object by simply looking at the question above?

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[FueledByRamen]

If it was floating it wouldn't read 4N in water.

 

[Sarahka74]

Would someone mind explaining this question in it's entirely? Why is the specific gravity = 36/27?

 

[MCATLasagna]

Hi,

If an object is sunken then
Weight/Force Bouyant = density object/density liquid.

In this case the weight is 36 N (in air). If the apparent weight in water is 9 N then the Force Bouyant is 36-9 = 27 N. (Weight apparent = weight real - force Bouyant)

Therefore going back to the first equation 36/27 = density object/density liquid. Density of liquid is 1 in this case so density of object = 1.33 and specific gravity also = 1.33

Going back to sunken vs. floating: the question will say floating or percent submerged. If it doesnt you can also recognize that a floating object would have an apparent weight of 0 as F Bouyant > mg

 

[BerkReviewTeach]

That is an AWESOME explanation MCATLasagna!

The only thing I might add is that given that the object has a weight in water (9N), it must have sank to the bottom to exert a force (weight). If it were floating, then it would 'feel weightless', because the buoyant force up would offset the weight down.