$A$ cyclist is riding with a speed of $36 \,km/h$. As he approaches a circular turn on the road of radius $50 \,m$, he applies brakes and reduces his speed at the constant rate of $0.5 \,m/s^2$. The magnitude and direction of the net acceleration of the cyclist on the circular turn are respectively:

• A
  $\frac{\sqrt{3}}{2} \,m/s^2, \tan^{-1}(4)$
• B
  $\frac{\sqrt{3}}{2} \,m/s^2, \tan^{-1}\left(\frac{1}{4}\right)$
• C
  $\sqrt{17} \,m/s^2, \tan^{-1}\left(\frac{1}{4}\right)$
• D
  $\frac{\sqrt{17}}{2} \,m/s^2, \tan^{-1}(4)$