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# M3 Circular Motion Watch

1. I'm a little confused with part b) of Ex. G question 7:

https://4cb73c3e1ece319eea2c1a4396b1...WJpMW8/CH4.pdf

I'm not sure why the resultant force can be greater or smaller than the centripetal force. How can the CF have a different value to the resultant forces causing it?

Thanks for any help!
2. Slipping in this instance refers to the particle rolling inwards towards the axis of rotation as opposed to remaining static at 3/5 a units away. Peace.
3. (Original post by WhiteGroupMaths)
Slipping in this instance refers to the particle rolling inwards towards the axis of rotation as opposed to remaining static at 3/5 a units away. Peace.

I still don't understand how the centripetal force can have a different value to the resultant force caused by the friction and the tension
4. (Original post by PhyM23)

I still don't understand how the centripetal force can have a different value to the resultant force caused by the friction and the tension
I don't understand what you're trying to say here, or how it relates to the question. Which resultant force are you thinking of?
5. (Original post by PhyM23)
TeeEm
what seems to be the problem?
6. (Original post by TeeEm)
what seems to be the problem?
I don't understand the logic behind the inequalities formed in the question. I understand the two possible scenarios with the friction acting towards or away from the centre, but I'm not sure how the tension+friction can be greater than the centripetal force, and how the tension-friction can be less than the centripetal force.
7. (Original post by PhyM23)
I don't understand the logic behind the inequalities formed in the question. I understand the two possible scenarios with the friction acting towards or away from the centre, but I'm not sure how the tension+friction can be greater than the centripetal force, and how the tension-friction can be less than the centripetal force.
there is no such thing as the centripetal force
this is a term used by physicists

8. (Original post by TeeEm)
there is no such thing as the centripetal force
this is a term used by physicists

It's 7b)
Attached Images

9. (Original post by PhyM23)
It's 7b)
I will do the question (with different numbers) and post a worked solution by late afternoon for you
10. (Original post by TeeEm)
I will do the question (with different numbers) and post a worked solution by late afternoon for you
Thank you very much
11. (Original post by PhyM23)
Thank you very much
Attached Images

12. (Original post by TeeEm)
PRSOM

Thanks, much appreciated. Is there a reason you took $\dpi{150} \ddot{r}$ to be acting outwards? Is this just convention?
13. (Original post by PhyM23)
PRSOM

Thanks, much appreciated. Is there a reason you took $\dpi{150} \ddot{r}$ to be acting outwards? Is this just convention?
this is the direction of r increasing
14. (Original post by TeeEm)
this is the direction of r increasing
Ahh that makes sense

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