Timeline for Worked Example - Classical Mechanics by David Morin
Current License: CC BY-SA 4.0
20 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jun 26 at 18:23 | history | edited | BioPhysicist | CC BY-SA 4.0 |
added 3 characters in body
|
| S Jun 26 at 18:22 | history | rollback | BioPhysicist |
Rollback to Revision 4 - Edit approval overridden by post owner or moderator
|
|
| Jun 26 at 17:55 | history | suggested | Sahil Muhammed | CC BY-SA 4.0 |
Corrected a sentence to convey the right meaning
|
| Jun 26 at 16:02 | review | Suggested edits | |||
| S Jun 26 at 18:22 | |||||
| Jun 25, 2020 at 12:32 | comment | added | BioPhysicist | @thornsword Yes, that appears to be the case | |
| Jun 25, 2020 at 12:28 | comment | added | thornsword | Okay, so in the end..the problem assumes that the boat is actually pulling on the rope..and we are trying to hold it and prevent it from slipping...am I correct? | |
| Jun 25, 2020 at 12:27 | vote | accept | thornsword | ||
| Jun 25, 2020 at 10:41 | comment | added | BioPhysicist | @thornsword I have edited my answer. After more thought I do agree that the problem could have been worded better to state certain assumptions. | |
| Jun 25, 2020 at 10:41 | history | edited | BioPhysicist | CC BY-SA 4.0 |
added 792 characters in body
|
| Jun 25, 2020 at 3:55 | comment | added | thornsword | As a counter example(showing why $dT>0$ cannot be assumed). Consider a fluid in a beaker. Let's try to derive the expression for the pressure in a static fluid. Consider a cylindrical portion of the fluid. Let us take the level of the base of the beaker to be $0$ in our $Y$ co-ordinate system. Now consider the blob of fluid in the chosen cylinder between $y$ and $y+dy$. Then the pressure in the fluid at a height $y$ is $P$, and the pressure at $y+dy$ is $P+dP$. Here, of course we cannot assume $dP>0$. Otherwise it would imply that pressure increases with increase in height from the base. | |
| Jun 25, 2020 at 3:44 | comment | added | thornsword | I understood the first part of your edited answer. But I don't see why we assume $dT > 0$? How can we make an assumption like that without knowing which force is larger? Secondly, I understood your point about inequalities...but the picture in my mind is, if something is pulling the other end with a very large force, then we need to apply only a sufficiently small force to balance it..I don't see how we can pull a huge boat by applying a small force...even if the equality doesn't hold, the range of possible values for the tension is still huge! | |
| Jun 24, 2020 at 18:34 | comment | added | BioPhysicist | @thornsword I have edited my answer. In response to your first comment, keep in mind that we are dealing with inequalities here, not actual force outputs necessarily. More turns just means we could have a larger maximum tension applied to the boat; it doesn't mean $T=T_0e^{\mu\theta}$ | |
| Jun 24, 2020 at 18:31 | history | undeleted | BioPhysicist | ||
| Jun 24, 2020 at 18:31 | history | edited | BioPhysicist | CC BY-SA 4.0 |
added 403 characters in body
|
| Jun 24, 2020 at 18:24 | history | deleted | BioPhysicist | via Vote | |
| Jun 24, 2020 at 18:24 | history | edited | BioPhysicist | CC BY-SA 4.0 |
added 403 characters in body
|
| Jun 24, 2020 at 17:40 | comment | added | thornsword | I have edited my question to make it more clear. Could you please take a look and post another answer (or edit the current one)? | |
| Jun 24, 2020 at 17:30 | comment | added | thornsword | What I mean in my first comment here is....if the boat is "already" pulling the rope...before we grab the other end of the rope...then..the minimum tension with which we have to pull the rope should be given by $T_{0} \ge Te^{-\mu \theta}$. To me, it seems as if the author is saying that if we grab one end of the rope, then wrap the rope around a pole and then attach the other end to a boat, then if we pull one end with a tension $T_{0}$, in the limiting case, the boat would be pulled by a tension $T_{0}e^{\mu \theta}$ | |
| Jun 24, 2020 at 17:17 | comment | added | thornsword | No....consider this..I have attached a rope to the boat, and wrapped the rope around a pole say 10 times. Let the friction coefficient be 0.5. Then does it mean that..if I pull the free end of the rope by say 1N, then the force on the boat would be $e^{0.5*2\pi * 10}$?? This is approximately $4.5 * 10^{13} N$! Doesn't make any sense | |
| Jun 24, 2020 at 17:04 | history | answered | BioPhysicist | CC BY-SA 4.0 |