Which of the following quantities are always zero in a simple harmonic motion?

(a). Sinθ

Direction of Force and acceleration is always same.

Therefore, it will always be Zero as Sin(0°) = 0

(b). Sinθ

Direction of Velocity and displacement is same, so this expression will also be zero.

Now,

As direction of Force and acceleration is always opposite to Displacement. This means θ = 180.

∴ Sin180° = 0

∴ Cross product of Displacement with Force and displacement with acceleration will always be Zero.

Hence, all four options are correct

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