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1. A uniform rod AB has length 3m and weight 120N. The rod rests in equilibrium in a horizontal position, smoothly supported at points C and D, where AC = 0.5m and AD = 2m. A particle of weight W Newton is attached to the rod at a point E where AE = x metres. The rod remains in equilibrium and the magnitude of the reaction at C is now twice the magnitude of the reaction at D.

(a) Show that W = 60/(1-x).
(b) Hence deduce the range of possible values of x.

I desperately need help here as my teacher hasn't been in recently so I don't really understand this as well as I should do, I need to hand this in tomorrow and I would really appreciate somebody explaining this to me as simply as possible, this question has already been answered back in 2006 but the answer was just the Maths with no explanation of what they were doing and I just got lost, so please, treat me like I'm stupid and help me!
2. (Original post by Niall Scruton)
A uniform rod AB has length 3m and weight 120N. The rod rests in equilibrium in a horizontal position, smoothly supported at points C and D, where AC = 0.5m and AD = 2m. A particle of weight W Newton is attached to the rod at a point E where AE = x metres. The rod remains in equilibrium and the magnitude of the reaction at C is now twice the magnitude of the reaction at D.

(a) Show that W = 60/(1-x).
(b) Hence deduce the range of possible values of x.

I desperately need help here as my teacher hasn't been in recently so I don't really understand this as well as I should do, I need to hand this in tomorrow and I would really appreciate somebody explaining this to me as simply as possible, this question has already been answered back in 2006 but the answer was just the Maths with no explanation of what they were doing and I just got lost, so please, treat me like I'm stupid and help me!
First thing to do in a lot of Mechanics is to sketch a diagram.

Then for part a), think about the two different ways you can resolve the forces (one is moments as you know already) and for another, think about how you could resolve vertically.

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Updated: November 1, 2015
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