In the given figure, a =15 m/s² represents the total acceleration of a particle moving in the clockwise direction in a circle of radius R = 2.5 m at a given instant of time. The speed of the particle is : 

5.7 m/s

a = 15 m/s² ; r = 2.5 m

Tangential acceleration : a_t = g sin 30 = 9.8 x 0.5 = 4.9

Radial acceleration : a_r = \(\frac{v^2}{r}\) = \(\frac{v^2}{2.5}\)

a = \(\sqrt{a_t^2 + a_r^2}\)

15 = \(\sqrt{4.9^2 + (\frac{v^2}{2.5})^2}\)

⇒ v = 5.9 m/s