HEY DEAR YOUR ANSWER IS HERE From the crossed chords PROPERTY, h(2R-h) = X2 but 2R>> h therefore 2h = x2 and so h = x2/2R (equation 1) now x = AK which is almost the arcAB = vt (equation 2)
Combining 1 and 2, h = (vt)2/2R (equation 3) h is the vertical FALL and so using s = 1/2 at2 = h (equation 4)
Then from (3) and (4) 1/2at2 = (vt)2/2R leading to a = v2/R Using F = ma then F = mv2/R