How the wave equation relates to Newton's Second Law of Motion

Rich667
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Homework Statement


Open Question 3.bmp

Homework Equations




The Attempt at a Solution



Open Answer 3.bmp

Any help with this would be greatly appreciated
 

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consider a small sting segment with (different) tension force vectors acting on each end, and write down Newtons second law in two orthogonal directions
 
I think the problem lies in the definition of F and acceleration a. In answer 3.bmp the F is defined as the tension in the rope, which is coaxial to the string, while the second derivative of y , the acceleration of an element with coordinate (x,y), is vertical to the string. Surely you can't say F=ma with F and a pointing to 2 different directions.
 
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