I seem to have problems finding time in SHM.
To find the time after projection, I know that either x=asinωt or x=acosωt needs to be used, so since R is projected away from O, it means that it is moving towards the equilibrium position, therefore I used x=acosωt to find the time.
The Attempt at a Solution
-L/4 = 3L/4 cos (√2g/L)t
t= (√L/2g) cos-1(-1/3)
But, the correct answer should be
Why can't cosine be used? Since it is moving towards the equilibrium position?
Also, for the equations x=asin(ωt+α) or x=acos(ωt+α)
I am not sure when is α needed to take into consideration.
So far, I never encountered any questions needing to find α, but I would like to know when is α needed.
Thanks very much in advance!