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First, pardons to all because I don't have a physics background and I'm probably using laymans terms.

What is the rebound angle of a circle striking a concave surface?

Assume the simplest case:

  • the circle (red) is not spinning
  • the circle does not compress
  • the arc (blue) does not deform
  • there's no friction
  • there's no energy lost in the impact

Here's my attempt at an illustration with a red circle moving in a blue circle traveling towards the blue circumference along the gold path and rebounding on an unknown green angle.

enter image description here

user50811
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  • Draw a tangent at the point of contact and then normal to the tangent at the point of contact. Then the idea of light reflection can be used, so reflected wave will be equal to incident. – L.K. Jun 20 '14 at 16:08

1 Answers1

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Depends on the size of the circles, but usually angle of incidence = angle of reflection (in this case to a line tangent to the circle at point of incidence).

jhobbie
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  • Won't it be to the perpendicular to the tangent at the point of incidence? – Gummy bears Jun 20 '14 at 16:21
  • Why would that be true? – jhobbie Jun 20 '14 at 16:22
  • The real question with circular walls is: what point on your object hits first? This can lead to some movement that people don't usually think of. – PipperChip Jun 20 '14 at 17:03
  • @jhobbie. So does the circle reflect as if it struck a non-curved line (tangent to the point of incidence)? – user50811 Jun 20 '14 at 17:15
  • @PipperChip I see your point. The circle might hit (probably will hit) the circular wall before the projected (gold) line. Thanks for the input! I can live with the simplifying assumption that the circle is a point so the contact always occurs on the gold path. – user50811 Jun 20 '14 at 17:15
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    Yes! It doesn't matter to the incident ball what the shape of the rest of the wall it hits is, just where it hits. – jhobbie Jun 20 '14 at 17:16
  • @jhobbie as the angle of incidence and angle of reflection is taken along the normal to the point of incidence. In this case the normal will be the perpendicular to the tangent of the circle, will it not? – Gummy bears Jun 20 '14 at 18:07
  • Why are they taken along the normal? They can be a lot of different angles – jhobbie Jun 20 '14 at 18:13