Find Arc Length of Particle Moving on Curve

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SUMMARY

The discussion centers on calculating the arc length of a particle moving along a specified curve defined by the equation r(t) = a(cos t + t sin t)i + a(sin t - t cos t)j for the interval 0 ≤ t ≤ 2π. The correct formula for arc length is established as the integral of the magnitude of the derivative of the position vector, |r'(t)|, rather than simply integrating r'(t). The user initially miscalculated the arc length due to incorrect application of the formula, leading to an erroneous result of zero instead of the expected 2π²a.

PREREQUISITES
  • Understanding of vector calculus, particularly vector functions and their derivatives.
  • Familiarity with the concept of arc length in parametric equations.
  • Knowledge of integral calculus, specifically definite integrals.
  • Proficiency in trigonometric identities and their applications in calculus.
NEXT STEPS
  • Review the derivation of arc length for parametric curves in calculus.
  • Learn how to compute the magnitude of a vector function, specifically |r'(t)|.
  • Practice integrating complex functions over specified intervals.
  • Explore applications of vector calculus in physics, particularly in motion along curves.
USEFUL FOR

Students studying calculus, particularly those focusing on vector calculus and arc length calculations, as well as educators seeking to clarify concepts related to parametric equations and integration techniques.

Cassi
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Homework Statement



Find the length of the path traced out by a particle moving on a curve according to the given equation during the time interval specified in each case.

The equation is r(t) = a(cos t + t sin t)i + a(sin t - t Cos t)j, 0</=t</=2pi, a>0

Homework Equations



Arc length = interval (r'(t)dt)

The Attempt at a Solution



I found the derviative of r(t) to be r'(t) = cost + tsint +atcost +sintt -tcost +atsint
Integrating this from 0->2pi I keep getting 0 because it is subtracting itself. The answer is supposed to be 2pi2a. What am I doing wrong?[/B]
 
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##\vec{r}(t)## is a vector as is its derivative. You can't simply erase the ##\hat{i}## and ##\hat{j}##.
 
And the formula for arc length (integral, not interval) is incorrect. The integrand is ##|\vec r'(t)|##.
 

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