Simple Harmonic Motion - Alevel M3

[mr bob]

This is probably a really easy question. But alas the answer has eluded me thus far. Anyway, here is the question:-

Points O, A and B lie in that order on a straight line. A particle P is moving on the line with S.H.M period of 4s, amplitude 0.5m and centre O. OA is 0.1m and OB is 0.3m. When t = 0, P passes through B traveling in the direction OB. Calculate the time when P passes A

I tried using the following equation to find the first part of the motion, B to amplitude.

X = a Sin(wt + 0.3)
0.2 = 0.5 Sin(0.5Pi t + 0.3)

and for the second part of the motion, amplitude to A:-

0.4 = 0.5 Cos(wt)

However i get nowhere near the correct answer of 1.46s when i add the two times together.

Any help would be greatly appreciated,
Thanks,
Rob

 

[Galileo]

Adjust the initial phase. The phase should be such that
X(0)=0.3 m. You added 0.3 (m?) to the phase.