Understanding about differentials?

  • #1

Homework Statement



Problem 7.29:

http://cas.umkc.edu/physics/wrobel/phy240/Homework 5.pdf

Homework Equations



dr= R d(theta)

The Attempt at a Solution



I don't understand how to get R d(theta) = dr from the last part of the question, any explanation about how it works is appreciated.
 

Answers and Replies

  • #2
38
0
It's a formula from radian measure. Basically if you have the angle [tex]\theta[/tex] in radians, you can find the arc length by the formula:
[tex]l=r\theta[/tex]
So if you have a differential amount of [tex]\theta[/tex], you can find a differential amount of arc length which is just [tex]dl=rd\theta[/tex]
 

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