$A$ particle of mass $m$, initially at rest, is acted upon by a variable force $F$ for a brief interval of time $T$. It begins to move with a velocity $u$ after the force stops acting. The graph shows $F$ as a function of time, where the curve is a semicircle with peak force $F_0$ at time $T/2$.

• A
  $u = \frac{\pi F_0^2}{2m}$
• B
  $u = \frac{\pi T^2}{8m}$
• C
  $u = \frac{\pi F_0 T}{4m}$
• D
  $u = \frac{F_0 T}{2m}$