Determining the value of a constant

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    Constant Value
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Discussion Overview

The discussion centers on determining the value of a constant in the context of kinematics equations, particularly in relation to the equation dx/dt = gt + constant. Participants explore how to identify whether the constant corresponds to initial position (x_0) or initial velocity (v_0), considering the physical context and units involved.

Discussion Character

  • Technical explanation, Conceptual clarification

Main Points Raised

  • One participant expresses familiarity with the kinematics equation but seeks clarification on how to determine the constant's value, questioning if it should be x_0 or v_0.
  • Another participant suggests using the physical description of the situation and emphasizes the importance of checking for consistent units as a method to resolve the question.
  • A later reply reiterates the importance of the physical description and unit consistency, indicating agreement with the previous point.
  • Another participant proposes that since the constant does not depend on time, it can be determined by evaluating the equation at t=0, suggesting that the constant corresponds to the velocity at that time.

Areas of Agreement / Disagreement

Participants generally agree on the approach of using physical descriptions and unit consistency to determine the constant, but there is no consensus on whether the constant specifically represents x_0 or v_0.

Contextual Notes

There are limitations regarding the assumptions made about the physical situation and the definitions of the constants involved, which remain unresolved in the discussion.

Calpalned
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Example 3 shows the derivation of one of the kinematics equations. I am quite familiar with it. At the part where it says dx/dt = gt + constant, how does one determine if constant = x_0 or v_0? Thank you.
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You use the physical description of the situation ... in this case, just checking the units are consistent should work.
 
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Simon Bridge said:
You use the physical description of the situation ... in this case, just checking the units are consistent should work.
That makes sense. Thanks!
 
Since the constant term does not depend on time - you can always find the expression for it by putting ##t=0## into the equation.
In your example ##v=gt+c## you get ##v(0)=c## ... because you understand from the physics, that the time derivative of displacement is velocity.
 

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