Skip to main content
Physics

You are not logged in. Your edit will be placed in a queue until it is peer reviewed.

We welcome edits that make the post easier to understand and more valuable for readers. Because community members review edits, please try to make the post substantially better than how you found it, for example, by fixing grammar or adding additional resources and hyperlinks.

Required fields*

9
  • $\begingroup$ Think about this: How much force is needed to maintain the original circular motion? Then, how do you reduce the radius to 0.5? $\endgroup$ Commented Jan 25, 2020 at 20:14
  • $\begingroup$ To maintain? I guess zero. To reduce the radius I have to apply a force that is perpendicular to the velocity vector, and it doesn't have to be an external force. $\endgroup$ Commented Jan 25, 2020 at 21:09
  • $\begingroup$ Circular motion requires a force directed toward the center, $F_c=mr\omega^2$. Also, think about the direction the particle moves as it is changing $r$ and whether work is done on the particle. Does the kinetic energy of the particle increase? $\endgroup$ Commented Jan 25, 2020 at 21:12
  • $\begingroup$ It spirals inwards, I guess its kinetic energy has to increase, and it explains why its linear velocity eventually doubles, but I don't really see why it changes because of spiraling. $\endgroup$ Commented Jan 25, 2020 at 21:26
  • $\begingroup$ Ok, does the velocity and therefore kinetic energy of the particle increase because when the radius is being reduced the velocity is not perpendicular to the force vector and it causes a change in the velocity of particle? $\endgroup$ Commented Jan 25, 2020 at 22:06