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

In a simple Harmonic motion, Force must be linearly proportional to the displacement.

Also, F = -kx

a = -ω^{2}x

(a).

Direction of Force and acceleration is always same. So, the

dot product will become positive as for <90° ,is positive.

So this expression is positive.

(b).

Direction of velocity and displacement is same so the expression will also be positive.

*(c).*

*Force* *is* *opposite* *to* *displacement.*

Dot product will become negative as for >90° ,is negative

So, this expression is negative

Again,

*(d)*

*Force* *is* *opposite* *to* *displacement* *so* *it* *will* *also* *be* *negative.*

Therefore, the option a and b are correct.

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