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# Edexel Jan 2002 Q7 help watch

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1. Can someone please help me figure out how the hell to do this question. I can't for the life of me figure it out.

Thanks
Chris
2. Pure? Stats? Mechanics? Decision?
3. OH god I'm sorry. It's Mech. My brain is fried:P
4. You are in luck, I have this paper on my desk!

7)a
Resolve forces vertically
R - 2.5(3/5) - 0.3g = 0
R = 4.44N

Resolve horizontally -->
2.5(4/5) - Friction = 0
F = 2.5(4/5) = 2N

F = mu*R
2 = 4.44mu
mu = 2/4.44 = 0.450

Values in bold are from using pythagoras.

7)b
Resolve forces vertically
R + 2.5(3/5) - 0.3g = 0
R = 0.3g - 1.5 = 1.44N

7)c
F = mu*R
Reaction has decreased therefore friction has decreased. Coefficient of friction remains the same.
Horizontal component of tension is unchanged.
Therefore no longer in equilibrium.
5. Thanks a million!!! I had my diagram all wrong. The resultant force was parallel to the string :|. Thanks again!

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Updated: January 11, 2005
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