Why is the radius of a twirling rope represented by Lcostheta instead of r?

  • Thread starter Thread starter indelible.eggs
  • Start date Start date
  • Tags Tags
    Radius Rope
AI Thread Summary
The discussion centers on understanding why the radius of a twirling rope is represented by Lcostheta instead of r. The rope is not horizontal but at an angle, which affects the radius of the horizontal circle created by the motion. The tension in the rope must be broken down into components to analyze the forces correctly. The radius is defined as the horizontal component of the rope's length, clarifying the confusion. Ultimately, the correct interpretation is that r represents this horizontal component, aligning with the physics of circular motion.
indelible.eggs
Messages
4
Reaction score
0
I'm having difficulty understanding why the radius is not represented by r, but Lcostheta , isn't the entire rope in the horizontal direction? There is something I'm missing. Thanks. (Hopefully I posted this correctly.)

Homework Statement


The problem is example 1 on http://physics.bu.edu/~duffy/py105.html
You have to click on Circular Motion on the left-hand side of the site.

Homework Equations



F=mv^2/r

The Attempt at a Solution



It has already been solved on the web site.
 
Last edited:
Physics news on Phys.org
The example indicates quite plainly that the rope is not horizontal, but at an angle. Do you not understand why this is so?
 
Perhaps I'm having difficulty understanding what is being described. The rope is at an angle twirling some object in a horizontal circle. I understand why the tension would need to be broken down into its components. But it seems that the radius of the horizontal circle is purely horizontal (even if the rope is not) thus the radius would be r. I suspect I'm asking a very simple question, but I'm just not getting it. Thanks
 
I think I understand now: We have the length of the rope so the radius of the rope can be described as the horizontal component of the length of the rope. Thanks for your help, it was hard for me to see.
 
Yes, your current understanding is correct. r is indeed the "horizontal component" of the rope.
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Back
Top