Collision -- why there is no parallel component?

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Discussion Overview

The discussion revolves around the nature of forces acting on a particle during an elastic collision with a wall, specifically addressing the presence or absence of a parallel component to the force exerted by the wall. The scope includes conceptual understanding and technical reasoning related to collisions in physics.

Discussion Character

  • Conceptual clarification, Debate/contested, Technical explanation

Main Points Raised

  • One participant questions why there is no parallel component to the force from the wall, despite the particle having a parallel velocity component.
  • Another participant argues that a parallel component to the force exists unless a frictionless wall is assumed, suggesting that this is often ignored in basic physics due to its minor effect.
  • Some participants assert that the parallel component is present but typically neglected in idealized scenarios.
  • There is a suggestion that considering different scenarios, such as a stretched wall or a collision with a large object, could help in understanding the presence of a parallel component.
  • One participant emphasizes starting with ideal cases and acknowledges that approximations, like the coefficient of restitution, are commonly used in physics.

Areas of Agreement / Disagreement

Participants express differing views on the existence of a parallel component to the force during the collision, with some asserting its presence and others suggesting it is typically neglected. The discussion remains unresolved regarding the treatment of this component in different contexts.

Contextual Notes

Assumptions about the wall's properties (e.g., frictionless vs. elastic) and the idealization of collisions are noted as limitations in the discussion.

Jzhang27143
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say that a particle collides elastically with a wall 60 degrees from the wall's normal. the force from the wall is along the wall's normal. My questions is why there is no parallel component to the force from the wall since the particles velocity had a parallel component.
 
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there will be a parallel component to the force on the ball/particle unless you're assuming a frictionless wall. In beginning physics this is usually ignored because it is a minor effect. This is easily verifiable - when you throw a ball and it bounces, it will spin. The spinning is caused by the parallel component of the force on the ball.

If you're talking solid state / particles / lattice interactions, that is beyond me.
 
There is parallel component but is being neglected.
 
yes there is parallel componet but is being neglected , if you imagine a stretched wall or the collision may be with a giant rock then we can understand
 
We take things a step at a time. Start with the most ideal case and work upwards - or leave it at that, if you want to. Even the coefficient of restitution, beloved of all students, is only an approximation but it does well in many cases.
 

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