Deceleration and Change of Direction

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Discussion Overview

The discussion revolves around a physics problem involving the acceleration of a baseball after being struck by a bat, specifically focusing on the calculation of acceleration when the baseball changes direction. The scope includes mathematical reasoning and conceptual clarification regarding the use of vectors and coordinate systems.

Discussion Character

  • Mathematical reasoning, Conceptual clarification

Main Points Raised

  • One participant proposes that the acceleration of the baseball is -5,000 m/s² based on their calculation.
  • Another participant suggests defining the positive direction as the direction of acceleration, resulting in a positive acceleration of 5,000 m/s² when using -20 m/s as the initial velocity and 30 m/s as the final velocity.
  • A third participant advises against using the term "deceleration" and emphasizes the importance of vector direction, suggesting that if the acceleration is negative, it indicates a decrease in velocity in that direction.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of acceleration and the use of terminology, indicating that there is no consensus on the best approach to describe the situation.

Contextual Notes

The discussion highlights the importance of defining coordinate systems and the implications of vector signs in calculations, but does not resolve the ambiguity in terminology and interpretation of acceleration.

joel amos
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A question from my textbook states:
A baseball moving at 20 m/s is struck by a bat and moves in the opposite direction at 30 m/s. if the impact lasted for 0.010 s, what was the baseball's acceleration?

Would the answer be -5,000 m/s^2?
 
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Yep, that works. However, since the coordinate system wasn't defined for you, why not define the positive direction to be the direction of the acceleration? If you define the initial velocity to be -20 m/s and final velocity to be 30 m/s, the acceleration is a positive 5000 m/s2.
 
it's a good idea not to use the word "deceleration" when you are working out these things. Use the idea of vectors - which have signs.
If you draw a big arrow on your (imaginary, perhaps) diagram to define the direction you will use for Positive, stick to it, and, if the acceleration comes out as negative then this means the velocity in that direction is decreasing. If you want to talk to 'Joe Public', at that point, you can then use the word "deceleration'.
 
Thanks guys
 

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