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Discussion Overview

The discussion revolves around the topic of 2D kinematics, specifically in the context of a physics course. Participants are addressing challenges faced by a newcomer in understanding the principles and applications of 2D motion, including vector decomposition and the influence of gravity.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • Paul expresses difficulty in grasping 2D kinematics and seeks pointers for understanding.
  • One participant suggests that the relationship between horizontal and vertical motion is independent, emphasizing the role of time and trigonometric functions.
  • Another participant requests clarification on specific problems to better assist Paul.
  • A participant provides formulas for breaking down vectors into components, associating the x-direction with cosine and the y-direction with sine.
  • Some participants challenge the assertion that y is always paired with sine, noting that context and specific angles can dictate the appropriate trigonometric function.
  • It is mentioned that 2D kinematics should not be limited to scenarios influenced solely by gravity, suggesting a broader application of the concepts.
  • Participants agree on the importance of breaking down vectors into one-dimensional components but debate the correct associations of sine and cosine based on the situation.

Areas of Agreement / Disagreement

There is no consensus on the correct pairing of sine and cosine with the x and y components, as participants present competing views on the conditions under which these associations hold true. The discussion remains unresolved regarding the generalization of 2D kinematics beyond gravitational influence.

Contextual Notes

Participants express varying assumptions about the application of trigonometric functions in 2D kinematics, and there are unresolved mathematical steps in the discussion of vector decomposition.

xXshortyXx
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Hey every one,
This is my first post on the forums glad to know i have such smart people here who can help me when I am stuck. right now I am taking physics 12 in British columbia. For some reason I am really having trouble grasping the topic of 2d kinematics. any pointers in helping me understand will be greatly apprecieated!

THX Paul
 
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I've always thought the whole gist of the thing went something like "Left and right have nothing to do with up and down except for time, and if you find something that appears to have both, it won't after a sine or cosine."

cookiemonster
 
Originally posted by xXshortyXx
Hey every one,
This is my first post on the forums glad to know i have such smart people here who can help me when I am stuck. right now I am taking physics 12 in British columbia. For some reason I am really having trouble grasping the topic of 2d kinematics. any pointers in helping me understand will be greatly apprecieated!

THX Paul

Well what specifically are you having trouble with. Maybe give an example problem.
 
With 2D kineamatics you must remember that the Y direction (up and Down) are only dependent on gravity and the range or X direction is only dependent on the intial velocity in that direction. The 2 forumulas should help.

X = r cos of the angle.
Y = r sin of the angle.

Always break these vectors down and then it is a plug and chug from then on.

Nautica
 
Er.. x is not necessarily paired with the cosine and y is not necessarily paired with the sine. It really depends on which angle you're talking about. Additionally, 2D kinematics is not limited to motion under the influence of Earth's gravity and really should be generalized beyond such a scenario.

It is good advice to always break 2D vectors into their 1D components, though, and you will do that with trig functions.

cookiemonster
 
If you will notice in my post I qualified my Y by saying it was up and down.

Nautica
 
Even so, y not always paired with the sine. Take, for instance, a swinging pendulum. The angle is usually taken to be between the y-axis and the rod. In such a case, the vertical is paired with the cosine.

I think it's better to just remember to separate components and to learn to choose the sine or cosine as appropriate.

cookiemonster
 
2d Equations

Y=Voyt-.5gt^2
Vy=Voy-gt
Vy^2=Voy^2-2gy
 

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