Timeline for Dynamics question. Please help, exam coming soon [closed]
Current License: CC BY-SA 3.0
20 events
| when toggle format | what | by | license | comment | |
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| Jun 16, 2014 at 16:41 | history | closed |
Colin McFaul John Rennie Brandon Enright BMS Kyle Oman |
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| Jun 16, 2014 at 3:49 | vote | accept | Pedro | ||
| Jun 15, 2014 at 17:38 | review | Close votes | |||
| Jun 16, 2014 at 16:41 | |||||
| Apr 14, 2013 at 16:03 | comment | added | Pedro | @Qmechanic You're right. I cannot think of a succinct title, can you? | |
| Apr 14, 2013 at 15:21 | comment | added | Qmechanic♦ | Comment to the title (v5): It would be good if OP (or someone else?) could make the title more descriptive of the physics problem. | |
| May 5, 2012 at 14:09 | comment | added | Ron Maimon | @PeterT.off: The most important thing for a rookie is not to be intimidated: if you don't understand, think a little, and if you still don't understand, skip! Try to formulate it as a recipe. The total "horizonal force" F (along the "curved" axis) divided by the total mass, gives the acceleration. The justification is that the pullies just redirect the force from one body to the other. | |
| May 5, 2012 at 2:09 | comment | added | Pedro | @Ron I'm an absolute rookie here, I can't see things so trivially like you! | |
| May 5, 2012 at 2:07 | comment | added | Ron Maimon | It's the same as for a free-falling object of mass M1+M2 with a force F as in my answer, the sum of the component of gravity along the two inclines, the part of gravity that isn't cancelled by the constraint forces. | |
| May 5, 2012 at 1:15 | comment | added | Pedro | @Ron I see. How would you determine the motion of block $1$ through time? | |
| May 5, 2012 at 1:12 | comment | added | Ron Maimon | @PeterT.off: The "constraint" forces are the normal forces and the tension--- they are completely determined by the fact that the blocks can't fall into the inclines and the fact that they have a fixed total distance between them along the rope. You just ignore the constraint forces. Please don't be scared off by me saying "Lagrangian", I just mean "energy conservation". In this case, just energy conservation determines everything. | |
| May 4, 2012 at 19:35 | comment | added | Pedro | @Ron What do you call a "constraint" force? This course is really elementary, so I don't think Lagrangian's will appear. It is basically Cinematics, Vectors, basic Dynamics, rectilinear movement (with constant speed or constant acceleration), and relative movements. | |
| May 4, 2012 at 19:28 | comment | added | Ron Maimon | @PeterT.off: It is justified by Lagrangian mechanics. You can find the same answer by calculating all the constraint forces by hand, but it does scream for a fundamental explanation. This is why Lagrangians take over in later classes. | |
| May 4, 2012 at 19:27 | answer | added | Ron Maimon | timeline score: 3 | |
| May 4, 2012 at 18:12 | comment | added | Pedro | @IshaanSingh Right. Is this "curving" of the axis a common practice when solving these type of problems? It seems so farfetched! | |
| May 4, 2012 at 18:11 | comment | added | Ishaan Singh | Now that you have the acceleration, use the fact $a=\frac{dv}{dt}$. It will get you a linear relation between time $t$, and velocity $v$. Or, you could use the equation of motions as well as the acceleration is constant. | |
| May 4, 2012 at 18:05 | history | edited | Pedro | CC BY-SA 3.0 |
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| May 4, 2012 at 17:53 | history | edited | Pedro | CC BY-SA 3.0 |
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| May 4, 2012 at 17:38 | history | edited | Pedro | CC BY-SA 3.0 |
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| May 4, 2012 at 17:25 | history | edited | Pedro | CC BY-SA 3.0 |
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| May 4, 2012 at 16:59 | history | asked | Pedro | CC BY-SA 3.0 |