A 0.300 kg object is suspended from the ceiling of an accelerating boxcar as in the figure below. The acceleration a = 2.90 m/s2I'm not sure how to do this problem, I tried using Newton's 2nd lawa) find the angle that the string makes with the vertical

b) find the tension in the string.

$\displaystyle \sum F = ma$ and go part b to be 8.526. Please help.