Timeline for Work-energy theorem and Newton's second law
Current License: CC BY-SA 4.0
5 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Nov 29, 2022 at 17:04 | comment | added | basics | Too many words, without a point here. 2nd law implies energy theorem, the implication in the opposite direction doesn't hold, and can't hold if the system has more than one d.o.f., as explained in the answer. And there is not even the need to introduce the concept of potential energy | |
| Nov 29, 2022 at 16:47 | comment | added | Cleonis | About the difference between the concept of potential energy and kinetic energy. While we can attribute a potential energy to a particular test object, it is very common to generally refer to a potential in the sense of a spatial distribution. Example: gravitational force is proportional to $\tfrac{1}{r^2}$, and the corresponding potential rises proportional to $\tfrac{1}{r}$ around the gravitating mass. The gradient I referred to is the gradient of that spatial distribution. Kinetic energy, on the other hand, is used only to express the state of motion of a particular object. | |
| Nov 29, 2022 at 0:10 | comment | added | basics | and the gradient of what give you the kinetic energy? | |
| Nov 28, 2022 at 23:48 | comment | added | Cleonis | Well, recovering the force vector directional information is straightforward, that underlines that the information is still available. Let's take the case with two degrees of freedom. I will refer to the spatial coordinates as $x$ and $y$. Then the potential energy is a function of both $x$ and $y$. To recover the force vector: for the force component in x-direction take the partial derivative with respect to $x$, for the force component in y-direction take the partial derivative with respect to $y$. Stated differently: the gradient of the potential energy function gives the force vector. | |
| Nov 28, 2022 at 22:43 | history | answered | basics | CC BY-SA 4.0 |