Question

Which among the following quantities, is always negative for a particle executing S.H.M.? (Symbols have their usual meaning)

• A. $\overrightarrow{r}.\overrightarrow{v}$
• B. $\overrightarrow{v}.\overrightarrow{a}$
• C. $\overrightarrow{a}.\overrightarrow{r}$
• D. $\overrightarrow{r}\times \overrightarrow{v}$

Answer 1

The correct option is C $\overrightarrow{a}.\overrightarrow{r}$

The phase angle between displacement and acceleration of a particle executing S.H.M. is $\pi$.

Therefore $\overrightarrow{a}.\overrightarrow{r}<0$