rod of Pyrex glass is precisely measured against an aluminum measuring stick at a temperature of 20°C, and the length of the rod is measured as exactly 25.0 cm. The temperature in the lab is then raised to 35°C for one hour, and then the Pyrex rod is measured a second time against the same measuring stick. The second measurement of the rod’s length can be expected to be:
A. 25.0 cm.
B. greater than 25.0 cm.
C. less than 25.0 cm.
D. less than or equal to 25.0 cm.
2007-11-16 09:03:52 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Engineering
C
The Pyrex changes very little with temperature change. However, The aluminum rod expands as it is heated giving making the rod to appear shorter.
2007-11-16 09:34:11 · answer #1 · answered by Tim C 7 · 0⤊ 0⤋
Previous answers are correct. CTE of Al is higher than CTE for pyrex so, both will be longer at the higher temp but, relative to the Al measuring stick, the pyrex will measure shorter than 25 cm (since the Al 25 cm mark is no longer 25 cm). The point on measurement error is also valid, if you do not look carefully, it will still look like 25 cm.
2007-11-16 17:59:06 · answer #2 · answered by Gary H 7 · 0⤊ 0⤋
so here we have two items and these two items are being subjected to a temperature change.
Our frame of reference is the measuring stick, but we must remember that it has also been subjected to the temp. change.
So we need to look up the CTE or Coefficient of thermal expansion of Aluminum and of Borosilic (Pyrex) glass.
Which of these two do you think has the greater CTE?
The greater the number the more the element will change in its dimentional axis.
I don't have the numbers, but I believe that the aluminum will change (or grow more) than the glass.
So this is a trick question in a way, because the measuring stick has become longer than it originally was to begin with.
The answer is C
accuracy also comes into play here, we are not given the accuracy of our measuring stick.
But the moral here is that the glass and the aluminum will have had dimmensional changes, its just that the aluminum will have changed dimensionally more than the glass.
2007-11-16 17:41:11 · answer #3 · answered by mixmaster2 3 · 0⤊ 0⤋
less than 25.0 cm
because upon heating Aluminium would try spread on sides then you will have less high rod
Also check the Thickness before and after heating
thickness may goes more...but check
thnks
2007-11-16 17:40:03 · answer #4 · answered by Vicks 2 · 0⤊ 0⤋