# M3 questionWatch

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#1
A bead B of mass 0.8kg is threaded on a smooth circular wire centre O and radius 0.4m which is fixed in a horizontal plane. A light inextensible string is attached to B and passes through a small smooth horizontal ring at O and carries a mass of 0.4kg which is hanging freely. B is moving on the wire with a constant speed of 5ms^-1. Calculate the magnitude and direction of the reaction of the wire on B. i don't know where to start! It's the last question of the exercise and is the only one I can't do.
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14 years ago
#2
(Original post by Widowmaker)
A bead B of mass 0.8kg is threaded on a smooth circular wire centre O and radius 0.4m which is fixed in a horizontal plane. A light inextensible string is attached to B and passes through a small smooth horizontal ring at O and carries a mass of 0.4kg which is hanging freely. B is moving on the wire with a constant speed of 5ms^-1. Calculate the magnitude and direction of the reaction of the wire on B. i don't know where to start! It's the last question of the exercise and is the only one I can't do.
Use the fact that the tension is equal in both parts of the string. IE, T=0.4g.
Use R for the reaction magnitude and let it act at an angle theta to the horizontal. You can then resolve horizontally and vertically for the particle in circular motion.
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#3
(Original post by Gaz031)
Use the fact that the tension is equal in both parts of the string. IE, T=0.4g.
Use R for the reaction magnitude and let it act at an angle theta to the horizontal. You can then resolve horizontally and vertically for the particle in circular motion.
could you draw a quick diagram?
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#4
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#5
Surely the reaction doesn't act at an angle? Doesn't it act inwards?
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14 years ago
#6
(Original post by Widowmaker)
Surely the reaction doesn't act at an angle? Doesn't it act inwards?
I'm sorry i can't draw and scan a diagram right now as i have to get ready and go to work.
It does act at an angle. It has to balance both the weight of the particle on the string and suppliment the tension in the string to give the particle it's circular acceleration.
Let the horizontal component be Rcos(theta). Let the vertical component be Rsin(theta).
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