Acceleration

The displacement of an object undergoing simple harmonic motion is given by X = Xmax cos ωt. Which expression in the key represents the acceleration of the object?
Ans:

A. Xmax ωcos ωt
B. -Xmax ωcos ωt
C. Xmax ω>2 cos ωt
D. -Xmax ω>2 cos ωt
E. Xmax ω sin ωt
F. -Xmax ω sin ωt
G. Xmax ω>2 sin ωt
H. -Xmax ω>2 sin ωt