TOLC-med 2022 Q 51

Practice Question Solving
1

The level of water contained in three identical glasses is exactly the same. However, while the glass 1 contains only water, in the glass 2 floats, partially immersed, a cork stopper and at the bottom of glass 3 there is a steel ball.
What can we say about the weights P1, P2, P3 of the three glasses measured by a scale?

A) P3>P1=P2
B) P3>P2>P1

Hi
the correct answer is A)
how can we rule out option B)? clearly the cork is lighter than water for it to float but it must have some mass, why is this not accounted for?

@AriHoresh

2

I think the cork has the exact same density as the water since it’s

therefore the mass missing from the absence of water is accounted for by the mass of the cork.

3

that makes sense but wouldn’t only the half of the cork that is immersed account for the missing mass of water?

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4

I think that the fact that it’s half immersed is meant to indicate that it has the same density as water, however the fact that the 2 glasses are at the same level indicates that they both have the same volume of material and so is the glass with the steel ball. So given they have the same volume and density, that implies they have the same mass.

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