Really nasty and evil mechanics question!

G

Guest

Guest
I dare anyone to take on this question who is doing Alevel maths!

2 small rings A and B are attatched to opposite ends of a light inextendible string. The rings are threaded on a rough wire which is fixed verticaly with A above B. A horizontal force P os applied at a point P. Both parts AP and BP are taut and the system is in equilibrium. The part BAP amkes angle a and ABP makes angle b. The weight of A is 2N and the tensions in the parts AP and BP are 7N and TN respectively. It is given that cosa = 0.28 and sina = 0.96 and that A is in limiting equilibrium. Find the coefficient of friction between the wire and ring A.

thanx alot

Alice :shock: :shock:
 
forces on ring A ...

f, friction
w, weight given as 2 newtons
T, tension in the string given as 7 newtons
N, normal force of the wire on the ring

in the x-direction ...

Tsin(a) = N
N = 7(.96) = 6.72 newtons

in the y-direction ...

f = w + Tcos(a)
F = 2 + 7(.28) = 3.96 newtons

since A is in limiting equilibrium, f is amaximum ...

coefficient of friction, u = f/N = 3.96/6.72 = approx .59

so ... what is this A-level "maths" of which you speak?
 
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