- #1
nysnacc
- 184
- 3
Homework Statement
Homework Equations
rXF ??
The Attempt at a Solution
T= 6 N (r =1)
T = 12 N (r=2)
Rotating disk find the radial and transverse velocity
- Thread starter nysnacc
- Start date
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Homework Help Overview
The discussion revolves around a problem involving a rotating disk, where participants are tasked with finding the radial and transverse (tangential) velocities as the disk spins and moves outward. The context includes considerations of forces, energy conservation, and the properties of an elastic string.
Discussion Character
- Exploratory, Conceptual clarification, Problem interpretation, Assumption checking
Approaches and Questions Raised
- Participants discuss the initial conditions of the disk's motion, including its tangential speed and radius. There are considerations of energy conservation and the role of tension in providing centripetal force. Questions arise about the contributions of elastic properties of the string and the validity of assumptions made regarding forces and motion.
Discussion Status
The discussion is active, with participants exploring various interpretations and approaches to the problem. Some guidance has been provided regarding the need for multiple equations to solve for the unknowns, and there is an emphasis on understanding the underlying physics before applying specific laws.
Contextual Notes
Participants note the importance of assumptions regarding the elastic string and the forces involved, indicating that these factors may influence the calculations of velocity. There is a recognition of the need to clarify these assumptions before proceeding with the problem-solving process.
rXF ??
T= 6 N (r =1)
T = 12 N (r=2)
- #2
Simon Bridge
Science Advisor
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So far so good - do you have a question?
Please describe how you are thinking about the problem ... given the initial condition, what do you think will happen?
Why is it important that the string is elastic (how would you model the string?)
Please describe how you are thinking about the problem ... given the initial condition, what do you think will happen?
Why is it important that the string is elastic (how would you model the string?)
- #3
andrevdh
- 2,126
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There is a lot going on in this problem and we have to make some (hopefully correct 
assumptions).
First the disk is spinning about the centre at 1 meter with a tangential speed of 4 m/s.
Then it motions out to 2 meter and they want both the radial and tangential speed when it is spinning about the centre at this distance.
What comes to mind is maybe trying energy conservation?
Energy is stored in the elastic as it is stretched, thankfully it obeys Hooke's law!
Also the tensions at the various radii supplies the centripetal forces for the spinning motion.
assumptions).First the disk is spinning about the centre at 1 meter with a tangential speed of 4 m/s.
Then it motions out to 2 meter and they want both the radial and tangential speed when it is spinning about the centre at this distance.
What comes to mind is maybe trying energy conservation?
Energy is stored in the elastic as it is stretched, thankfully it obeys Hooke's law!
Also the tensions at the various radii supplies the centripetal forces for the spinning motion.
Last edited:
- #4
nysnacc
- 184
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Simon Bridge said:
I mean what does those contribute to the finding of v?
Can I just use F= m V2 / r which i put F = T at 0.25m, and r = 0.25m ... so that V is the Vtheta??
- #5
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Conserving mechanical energy is a good starting point and gives you one equation. You need to find two quantities so you need a second equation. What else is conserved? Hint: The force on the mass is along the radius.andrevdh said:
- #6
Simon Bridge
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mv^2/r is the centripetal force needed to keep the disk in circular motion... what could be providing the centripetal force, and does it provide that much?nysnacc said:
Note: the other two are jumping ahead. You need to understand the motion before deciding on what laws to use, and what assumptions are valid.
Nysnac's assumptions may not be valid, and how kuruman's modification works will depend on that.
So let's start with understanding the physics...
... post #2 asks a bunch of questions, please answer them.
- #7
andrevdh
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When an object, p, moves along a curved path its velocity v can be broken into two components, a radial component vr and a tangential component vt
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