Confused abt derivation of centripetal acceleration

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Discussion Overview

The discussion revolves around the derivation of centripetal acceleration, specifically focusing on the relationship between the arc length and the chord length in the context of isosceles triangles. Participants are exploring the meaning of the notation s tending to c and its implications in the derivation process.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the statement that the arc length s tends to the chord length c, noting that the tangential velocity at point A is not directed towards c.
  • Another participant seeks clarification on the meaning of s→c, suggesting that it indicates the arc length getting close to the chord length.
  • There is a discussion about the relationship between the arc and chord lengths, with some participants asserting that they approach the same value as certain conditions are met.
  • One participant challenges the idea that the arc length tends to the chord length, stating that they simply take a specific value for both.
  • A later post introduces a mathematical approach involving the area of an isosceles triangle and limits, suggesting that as θ approaches 0, c approaches s.

Areas of Agreement / Disagreement

Participants express differing views on whether the arc length s tends to the chord length c, with some asserting that they do get close while others contest this notion. The discussion remains unresolved regarding the interpretation of these lengths in the context of centripetal acceleration.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the arc and chord lengths, as well as the conditions under which they are considered to be approaching one another. The mathematical steps presented are not fully resolved, leaving some ambiguity in the derivation process.

toforfiltum
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A comparison of corresponding parts of these two similar isosceles triangles yields

cc7ee24b-30e0-4cc9-80e2-47c7f4d1086b.gif

cce1bb03-f244-4e0f-a7d9-240c4cc0e010.gif

velocity triangle
displacement triangle

4562c164-1631-4934-9267-96a3a33872d1.gif


where

|-vo| = |vf| = v
In a small time interval Δt, the arc length s → c.


Okay, so I got this from Physics LAB, and I don't understand the last statement that states s tending to c. How could s even tend to c when the tangential velocity at A is not even directed towards c?
 
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toforfiltum said:
How could s even tend to c when the tangential velocity at A is not even directed towards c?

Do you understand what s→c means ?
 
Qwertywerty said:
Do you understand what s→c means ?
Not really, just that s is the arc and c is the cord. So I think that means the length of s gets very close to that of c.
 
toforfiltum said:
So I think that means the length of s gets very close to that of c.

Yes , it means that the length of the arc and the chord almost reach the same value ( obviously with arc greater than chord , but still getting close to the same value ) .
 
Qwertywerty said:
Yes , it means that the length of the arc and the chord almost reach the same value ( obviously with arc greater than chord , but still getting close to the same value ) .
Well, I don't get why the length of the arc tends to that of the chord.
 
toforfiltum said:
Well, I don't get why the length of the arc tends to that of the chord.

It doesn't , we just take such a value of arc and chord .
I'm sorry , do you know what a tangent is ?
 
Qwertywerty said:
It doesn't we just take such a value of arc and chord .
I'm sorry , do you know what a tangent is ?
A straight line that is perpendicular to one point in a circle.
 
Well, calculate the surface of triangle and compate it to the arc,you have an isocele triangle, the height of this triangle is h = r*cos(θ/2),It's surface is S = r2sin(θ)/2, now take this as θ→0 c = S/h = r2sin(θ)/(2*r*cos(θ/2)), use the fact that sin(θ) = 2*cos(θ/2)*sin(θ/2), c = r2sin(θ)/(2*r*(sin(θ)/2sin(θ/2)) = 2*r*sin(θ/2) = rθ = s, thus as θ → 0, c→s
 

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