Quiz - Physics - Volume/Pressure

[jonhall]

Both steel and aluminium expand significantly

Thermal expansion of metals does occur, but significantly (steel/auminum)? If I could see the change - now that would be significant!!

the pedantically correct answer

Good one!!

If I were back in my middle school science teaching days, there is a best choice to the question.

 

[saxman242]

You are a slave to minor effects and decimal points.

We're all slaves to physics

 

[Angelo Farina]

LOL. You are a slave to minor effects and decimal points. What is the major effect of the heating? Which answer is the most correct?

The linear thermal expansion coefficient of aluminium is 24E-6 K-1, so the volumetric expansion coefficient is approximately 3 times larger. For a temperature variation of 40 K (40 °C), the percentage variation of volume will be :
DeltaV/V = 3*24E-6*40 = 0.29% . Small, but not entirely negligible...
So also answer a) was definitely true.
The correct answer had be that both a) and c) were true.
More precisely, in both balloon and cylinder volume and pressure both increase. In the balloon, there is some small increase of pressure and a large increase of volume. In the cylinder, there is some small increase of volume and a large increase of pressure.

 

[saxman242]

That aluminum tank picks up a whole half a cubic inch of volume going from room temperature to outside on a 100 degree F day. Even more if it's sitting in direct sunlight.

 

[rhwestfall]

Where did it say it was an aluminum tank?

 

[Aviyes]

Argument could be made for either a or c. But, since a tank fill is typically measured by its pressure and not volume. While, the balloon would be measured by a noticeable change in its shape (volume change). The most correct answer is c.

 

[Angelo Farina]

Where did it say it was an aluminum tank?

If it was steel, the thermal expansion coefficient had been half that of aluminium, but the concept is the same. Metals expand significantly with heat...
In these "binary logic" questionnaires, there is not anything being "more" or "less" correct.
Each enunciate is either True or False. And here we have two enunciates which are both entirely true.
Said that, I also answered c), because is what I guess an instructor would expect me to answer.
However, if a student answers a) and is rejected, he has any reason of the world for appealing against the verdict, as a) is entirely true, too, and it was not possible to tick both a) and c)...
For making c) the only correct answer it had been necessary to declare "increase significantly", and not just "increase", both for the volume and for the pressure.

 

[rhwestfall]

Oh, I certainly saw the problem from the start with the questions......

 

[tursiops]

What is the major effect of the heating?

The linear thermal expansion coefficient of aluminium is 24E-6 K-1, so the volumetric expansion coefficient is approximately 3 times larger. For a temperature variation of 40 K (40 °C), the percentage variation of volume will be :
DeltaV/V = 3*24E-6*40 = 0.29% . Small, but not entirely negligible...
So also answer a) was definitely true.
The correct answer had be that both a) and c) were true.
More precisely, in both balloon and cylinder volume and pressure both increase. In the balloon, there is some small increase of pressure and a large increase of volume. In the cylinder, there is some small increase of volume and a large increase of pressure.

Don't you just hate it when someone goes on at length to answer a rhetorical question?

 

[rhwestfall]

verbal diarrhea...