Solving Confusions on Pulling a Spool

  • Thread starter Thread starter member 731016
  • Start date Start date
Click For Summary

Homework Help Overview

The discussion revolves around the dynamics of a spool being pulled, focusing on the application of forces such as static friction and the implications of motion without slipping. Participants are exploring concepts related to rotational motion, work-energy principles, and the kinematics of the spool's movement.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are questioning the applicability of uniformly accelerated motion (UAM) equations to the spool's motion, particularly regarding the role of static friction and the displacement of the point of application of forces. There are discussions about the distances moved by the hand and the spool, and the implications of rotation without slipping.

Discussion Status

The discussion is active, with participants providing insights and clarifications about the nature of static friction and its role in the problem. There is an ongoing exploration of the distances involved in the motion of the spool and the hand, with some participants expressing uncertainty and seeking further explanation.

Contextual Notes

Participants are navigating through various assumptions about the motion of the spool, including the effects of static friction and the definitions of displacement in the context of work done. There is a focus on understanding the relationship between the forces acting on the spool and the resulting motion.

  • #91
haruspex said:
Yes,

No, you are free to define positive separately for each force, each displacement, each acceleration. Just be clear about it and do it consistently through the equations.

If all such variables are along the perpendicular axes, it is a good idea to pick one convention for them all. If not, you could decompose each oblique variable into such components or define the conventions individually.

Many prefer to guess which way each will act and define positive accordingly. That's ok as long as you handle each consistently and accept that some may turn out to have negative values.

That said, there may be cases where the equation does change if you guessed wrongly, but I can only think of quite contrived ones.
Thank you for your reply @haruspex! That is very interesting!

Many thanks!
 

Similar threads

Motion of a spool of thread on an inclined plane related to inertia
  • · Replies 30 ·
2
Replies
30
Views
4K
Rotating spool on table with friction
  • · Replies 12 ·
Replies
12
Views
5K
Ball on a string thrown around a spool
  • · Replies 3 ·
Replies
3
Views
1K
Friction and an object stopping
  • · Replies 12 ·
Replies
12
Views
3K
Distribution of Energy when work is done on a system of 2 masses connected by a spring
  • · Replies 17 ·
Replies
17
Views
2K
The block and spool problem (dynamics of rigid bodies)
  • · Replies 13 ·
Replies
13
Views
6K
Rotating and translating spool across a table
  • · Replies 2 ·
Replies
2
Views
3K
Net work and kinetic energy (pushing a wagon to accelerate it)
  • · Replies 1 ·
Replies
1
Views
1K
Find the speed of the biker at the bottom of the hill
  • · Replies 38 ·
2
Replies
38
Views
4K
Solving Block & Spool: Finishing Line & Work-Energy
  • · Replies 3 ·
Replies
3
Views
7K