Struggling with constrained motion of connected particles

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Imperiosus
Hi everyone!

Really struggling with this question here, was hoping someone could point me in the right direction?
https://puu.sh/xVitw/4c0b89c576.png

1. Homework Statement

Set origin to bottom right.
OA is y (Which using cos(60)*R you can determine to be 0.5R).
OB is x (which you can determine using Pythagorean (2R)^2 = (0.5R)^2 + x^2 x =sqrt(3.75).
We are told in the problem that the speed of b is 2m/s.

Homework Equations


[/B]
L^2 = x^2 + y^2
Differentiate everything Note a=velocity of x and b = velocity of y in the y direction
0= 2xa + 2yb

The Attempt at a Solution


We know the velocity of x is 2
0= 2(sqrt3.75)(2) + 2(0.5)(b)

b=7.745 and using trig i get 8.944 for the speed of y total. (7.745/sin60)

According to the back of the book, the answer is 2.76, so clearly I am doing something very wrong!

Any help is appreciated, Thanks!
 
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