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Question
Which of the following quantities are always negative in a simple harmonic motion?
(a) \[\vec{F} . \vec{a} .\]
(b) \[\vec{v} . \vec{r} .\]
(c) \[\vec{a} . \vec{r} .\]
(d)\[\vec{F} . \vec{r} .\]
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Solution
(c) \[\vec{a} . \vec{r} .\]
(d)\[\vec{F} . \vec{r} .\]
In S.H.M.,
F = -kx
Therefore,
\[\vec{F} . \vec{r} .\] will always be negative. As acceleration has the same direction as the force,
\[\vec{a} . \vec{r} \] Will also be negative , always .
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