# How fast to spin object hanging by thread to break thread

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1. Feb 13, 2016

### Nikki1357

1. The problem statement, all variables and given/known data
If an object is hanging by a thread, how fast must it be twirled around in order to break the thread? (must also provide explanation of why this is the velocity).
As a part of a lab, pick a certain mass. Attach to light string (easily breaks) and pull the string through a cylindrical tube with blunt edges that won't cut the string. Spin mass in circle and reduce the radius, thus increasing the velocity, until mass breaks.

2. Relevant equations
F=mv^2/r
F=mw^2r
v=vo+at
v=wr
v/r=w

3. The attempt at a solution
If videotaped I know I can find the radius. I will be able to weigh a mass. I need help understanding the quickest way to measure acceleration. If I know the acceleration my plan it to time it to find when the mass breaks off and then use the 3rd equation from above to solve for the velocity (knowing it starts from rest).

2. Feb 14, 2016

### Nidum

Draw a diagram showing the geometry of the problem and mark in all the information that you think is relevant .

3. Feb 15, 2016

### Nidum

@Nikki1357

I see that you have been back for a look but not posted any reply . Does this help at all ?

The original question is badly worded and this may be causing you some needless difficulties .

Last edited: Feb 15, 2016
4. Feb 21, 2016

### Nikki1357

Hello. Sorry for not replying, but now I have a theoretical relationship between the variables involved. When I solve this equation mass is eliminated, but I know that increasing the mass will lead to a lower velocity and it must be included in the equation. I don't understand where I went wrong in my calculations. Please help!