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OCR M3 circular motion with variable speed question watch

1. Hi
I think I'm okay with this topic on circular motion as a whole, however I'm just a little bit stuck on how to put the coefficient of friction into this. I've only come across it within the limiting friction formula from M1, or the tan of the angle an object starts to slide. Help would be extremely appreciated as I'm self teaching this module. Thanks!
2. (Original post by Astronemma)
...
Intrinsically, it's no different to a standard friction question.

Start by working out the normal reaction on the bead?

Then what's the retarding force due to friction?

Hence what's the deceleration?

And your equation follows almost immediately.

Have a go and see how far you can get.
3. (Original post by ghostwalker)
Intrinsically, it's no different to a standard friction question.

Start by working out the normal reaction on the bead?

Then what's the retarding force due to friction?

Hence what's the deceleration?

And your equation follows almost immediately.

Have a go and see how far you can get.
There's zero gravity though, so the bead has no weight, so what's the normal reaction? That's what I don't get about this :/ without the link to force I have no idea how to link it into the equations of circular motion. Sorry if I'm missing something obvious here.
4. (Original post by Astronemma)
There's zero gravity though, so the bead has no weight, so what's the normal reaction? That's what I don't get about this :/ without the link to force I have no idea how to link it into the equations of circular motion. Sorry if I'm missing something obvious here.
You have motion in a circle.

Hence there is a force acting on the bead towards the centre of the circle. Standard equation for motion in a circle.
5. (Original post by ghostwalker)
You have motion in a circle.

Hence there is a force acting on the bead towards the centre of the circle. Standard equation for motion in a circle.
Of course! Thank you, I can't believe I missed that! It seems so easy now...
6. (Original post by Astronemma)
Of course! Thank you, I can't believe I missed that! It seems so easy now...

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