Q10

A particle moves with simple harmonic motion with equation $x=a\sin nt$. It first returns to its starting point after $\frac\pi3$ seconds and is travelling at $15$ m/s forwards at this time. The displacement of the particle is given by

A. $x=\frac52\sin6t$

B. $x=-\frac52\sin6t$

C. $x=5\sin3t$

D. $x=-5\sin3t$