Help 2-dimensional motion, with a bounce

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    Bounce Motion
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Discussion Overview

The discussion revolves around the mechanics of a ball launched in two-dimensional motion, specifically focusing on the angle of bounce after landing and the determination of new vertical velocity. The scope includes theoretical considerations of projectile motion, elastic collisions, and the effects of external factors like air resistance and friction.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant inquires about calculating the bounce angle and new vertical velocity after a ball is launched and lands a distance x away.
  • Another participant suggests using the arctan function to find the launch angle and states that, in the absence of air drag, the landing angle equals the launch angle. They propose that the x velocity remains constant if there is no friction.
  • This participant also notes that the new y velocity depends on whether the bounce is perfectly elastic or not, indicating that a bounce efficiency factor may be necessary to determine the new y velocity.
  • A third participant asserts that if the ball lands at the same height from which it was launched, the angle of impact and bounce will be the same as the initial launch angle, assuming no air resistance and a perfectly elastic bounce.
  • This participant further claims that the vertical velocity at the moment of bounce will equal the initial vertical velocity due to conservation of energy.

Areas of Agreement / Disagreement

Participants present multiple viewpoints regarding the conditions affecting the bounce angle and new vertical velocity. While some agree on the relationship between launch and bounce angles under ideal conditions, others introduce the complexities of air resistance and elasticity, indicating that the discussion remains unresolved with competing models.

Contextual Notes

Assumptions about the absence of air resistance and friction are critical to the claims made. The discussion also highlights the need for specific coefficients related to elasticity and resistance to fully resolve the problem.

Stellar
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If a ball is launched from a launcher at a height h and an angle theta and it lands x meters away from its original x position, and bounces, how can I figure out the angle at which it bounces? How does it relate to what I know? And how do I find the new y velocity?
 
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You should find the launch angle with the arctan of h/(x/2). If you have no air drag the landing angle is the same. So, if you find the angle you can find the x and y velocities when the ball lands. If there is no friction the x velocity remains the same. To find y velocity you must know if the bounce is perfectly elastic or not. If it is, then the new y velocity is the landing velocity. If not, you should have some bounce efficiency and so you can easiliy find new y velocity. Then you have x and y and you find the angle.
Bye
 
Assuming that the ball lands at the same height at which it started, then the angle at which it hits the pavement is the same as the initial angle! Furthermore, the angle at which it bounces will be the same angle: theta.

(That's also assuming no air resistance and that the "bounce" is perfectly elastic. If neither of those is true then you can't do the problem without knowing the coefficients of resistance and elasticity.)

In that case, by conservation of energy, the velocity y when the ball bounces is also exactly the same as the initial velocity!
 
Thank you!
 

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