What Are the Key Differences Between 2D and 1D Projectile Motion?

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Discussion Overview

The discussion explores the differences between 2D and 1D projectile motion, particularly focusing on the implications of object shape and rotation on trajectory calculations. It encompasses theoretical considerations and the effects of external factors like air resistance.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether the calculations for the trajectory of a 2D object, such as a square, are more complicated than those for a 1D object like a baseball.
  • Another participant asserts that if air resistance is ignored, the projectile motion is fundamentally the same for both 1D and 2D objects.
  • Discussion includes the concept of the center of mass, with a participant noting that all mass is concentrated at this point for calculations.
  • Concerns are raised about the implications of rotation for a 2D object, questioning if the equations differ from those for a 1D object.
  • A participant explains that while angular momentum is conserved in the absence of air resistance, the effects of air resistance are significant for rotating objects, leading to different trajectories in real-world scenarios.
  • Another participant emphasizes that from a kinematic perspective, the analysis focuses on the center of mass, suggesting that the differences may be more relevant in dynamics.

Areas of Agreement / Disagreement

Participants express differing views on the complexity of trajectory calculations for 2D versus 1D objects, particularly regarding the effects of rotation and air resistance. The discussion remains unresolved with multiple competing perspectives on the implications of these factors.

Contextual Notes

Limitations include assumptions about air resistance being negligible and the focus on the center of mass without fully addressing the complexities introduced by rotation and external forces.

Dirac1238
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I was just wondering is there any major difference between the projectile motion of a 2D object vs the projectile motion of a 1D object or just a point. For example in a 2D world if someone just threw a square, would the calculation of the trajectory be a lot more complicated then calculating a simple regents physics problem involving someone throwing a baseball?
 
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Not at all, its exactly the same if you're ignoring things like air-resistance, etc.
 
In every object there is a point ( center of mass ) that is acting as the whole mass of that object is concentrated in it.
 
vlado_skopsko said:
In every object there is a point ( center of mass ) that is acting as the whole mass of that object is concentrated in it.
yes but what if the 2D square was rotating, would the equation of rotation be different then for let's say a 1D line.
 
Dirac1238 said:
yes but what if the 2D square was rotating, would the equation of rotation be different then for let's say a 1D line.

GOOD QUESTION! :smile:

As long as we disregard air resistance, then a thrown object will conserve angular momentum, because the only acting force upon the object, gravity, works at the C.M of the object.

Thus, whatever energy associated with the object's rotation initially will be the same during the whole object's flight.

We can, therefore, ignore the object's rotational state when calculating its trajectory.


However, and this is important:
Air resistance is IMMENSELY important in order to describe the actual orbit of, say, a rotating baseball.
This is because the rotation of the ball creates a velocity differential in the ambient air, and therefore, a pressure differential upon itself as well.

This means that in a viscous fluid like air, a rotating ball will get quite a different course than the one predicted for a ball in vaccuum, rotating or not.
 
If by equation of rotation you mean angular momentum or angular kinetic energy of the bodies, it is in the field of dynamic, where objects must have mass associated with them and geometry (3d). And from kinematic point of view all the objects are the same because we only look at the center of mass of those objects and arildno explained that very well.
 

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