HARD Physics Problem!! I need your help please!!?

Question

In a physics experiment, a student places .3703 kg of copper in an insulated plastic tube 1.49 m long. The tube is inverted 373 times by the student. Assuming that the tube does not absorb any of the energy, what is the temperature increase of the copper in deg C?

How would you do this if they do not give you the original temperature of the copper??

Answer 1

You need to find the specific heat of copper. You probably also need to assume that the inversion occurs by rotation about the tube's midpoint, and that the copper does not slide from one end to the other until the inversion has been completed. This is because the manner of the inversion can affect the energy significantly.

Under these assumptions, the energy transferred into the copper is approximately the gravitational potential energy associated with a 1.49m change of height for a 0.3703 kg copper. This is 1.49 x 0.3703 x 9.81 = 5.413 joules. If this is done 373 times, then the total energy transferred to the copper is 373 times this, which is 373 x 5.413 = 1913.5 joules.

Let us suppose that the specific heat of copper is 385 J/kg per deg C. Then since you have only 0.3703 kg, this means that an energy input of 385 x 0.3703 = 142.6 J will heat your copper up by 1degC.

Since you are providing 1913.5 J, it will heat your copper up by 1913.5 / 142.6 = 13.4 degC. Which is probably the answer your teacher is looking for.

However, to complicate matters, if the tube is inverted very slowly and the copper slides down as soon as the tube is half inverted (ie horizontal), then only haf the energy is involved. In this case, the copper would heat up by only half as much.

I hope my arithmetic is ok! It looks like quite a large increase of temperature.

Answer 2

Clue: Forget about the oringal temperature. Pick one.... then just do the math to look for the increase. That is the key word... how much did it increase.

This is a very general problem, obviously if you had a starting temperature of extreme hot or cold, the problem would be bogus to begin with, but the objective here is to understand how the inversion of the tube affects the change in temperature. I would pick a number that is easy to work with. A whole integer for example.

Answer 3

You absolutely have to know HOW the tube is inverted. If you hold it at the top and turn it upward quickly, the weight will drop 2*1.49 = 2.98 m with every inversion. If you hold it at the middle, it will drop only 1*1.49 = 1.49 m per inversion. This will throw the answer off by 50%........
Other than that, Ricky's approach is sound in principle.

Answer 4

well, the copper has fallen through 313*1.49 meters, and therefore has converted m*g*h=0.3703*9.8*313*1.49 of potential energy into heat (joules). The temp change is heat/(mass*heat capacity of copper)