The Force Behind a Curve Ball: Spin and Projectiles

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Discussion Overview

The discussion revolves around the forces acting on projectiles due to their spin, specifically in the context of a baseball curving when thrown as a curve ball. Participants explore the terminology and concepts related to this phenomenon, including the Magnus effect and aerodynamic forces.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant mentions that projectiles experience a force due to their spin, asking for the name of this force.
  • Another participant suggests it is best referred to as lift.
  • A third participant clarifies that the Magnus effect describes the phenomenon but is not a name of a force, suggesting "lift" or "side force" depending on the frame of reference.
  • Further elaboration on the Magnus effect includes a description of aerodynamic forces, distinguishing between lift and drag based on their directions relative to the object's travel.
  • A participant confirms the term Magnus effect, expressing uncertainty about the terminology used by their professor.

Areas of Agreement / Disagreement

Participants express differing views on the terminology used to describe the force acting on the projectile, with some favoring "lift" and others discussing the Magnus effect without consensus on a definitive term.

Contextual Notes

The discussion includes various interpretations of aerodynamic forces and their components, highlighting the complexity of definitions and the dependence on frames of reference.

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The other day, my professor mentioned projectiles have a force on them due to their spin. The example he gave is how a baseball curves because of the spin of a curve ball. What's the name of this force?
 
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Magnus effect covers this in the general sense. It is not a name of a force though. Like Russ said, it probably is best to just call it lift or a side force depending on your frame of reference.

http://en.wikipedia.org/wiki/Magnus_effect
 
Another description of Magnus Effect, based on detachment of air flow:

http://www.geocities.com/k_achutarao/MAGNUS/magnus.html

The force is an aerodynamic force. By definition, lift is the component of aerodynamic force perpendicular to the direction of travel (with air as the frame of reference), and drag is the component of aerodynamic force in the direction of travel. Regardless of the method used to create the aerodynamiic force, Newton's 3rd law applies, forces only exist in pairs. The aerodynamic force exerted by the air onto an object is coexistent with the object exerting an equal and opposite force to the air, and the air responds to the force exerted by the object according to Newton's 2nd law, force = mass times acceleration.
 
Last edited:
Magnus effect! That's what he called it. I thought he said magnus force but I may have misheard him. Thanks!
 

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