00:01
Hi there, so for this problem, we are told that under the right conditions, it is possible due to surface tension to have metal objects float on water.
00:13
So we need to consider placing a short length of a small diameter steel that has the following density, carnicle that density sitment, that is 490 pounds.
00:35
Per cubic feet.
00:39
Rod and a surface of water.
00:41
So the question in this is what is the maximum diameter that the rod can have before it will sink.
00:50
Now we need to assume that the surface tension forces advertently upward.
00:58
And we are also told that a standard paper clip has a diameter of 0 .036 inches, partially in full a clip and see if we can get it to float in water.
01:14
So with that set, we're going to start with the following, so we can draw the situation that we have in here.
01:24
This is the route that we need to float.
01:27
They are going to spiriting two forces up and its weight.
01:33
We know that the forces up is equal to sigma times l, it equals in here, when l is the rod length.
01:52
Now, with this, we know that in order for the rot to float, it follows that 2 times sigma times the length should be greater than the weight or equal to the weight, which should be equal to pi over 4, times the diameter square, and this times l times the density for steel in this case.
02:23
Now, for the limiting case, we will have that the diameter, the maximum diameter that this can have, the square of that should be equal to two times the sigma times the length l...