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6.System of Particles and Rotational Motion
medium
A disc is rotating with angular velocity $\vec{\omega}$. A force $\vec{F}$ acts at a point whose position vector with respect to the axis of rotation is $\vec{r}$. The power associated with torque due to the force is given by ..........
A
$(\vec{r} \times \vec{F}) \cdot \vec{\omega}$
B
$(\vec{r} \times \vec{F}) \times \vec{\omega}$
C
$\vec{r} \times(\vec{F}, \vec{\omega})$
D
$\vec{r} \cdot(\vec{F} \times \vec{\omega})$
Solution
(a)
$\text { power } =\vec{F} \cdot \vec{v}$
$=\vec{F} \cdot(\vec{r} \times \vec{w})$
$=[\vec{F} \vec{r} \vec{w}]$
$=[\vec{r} \vec{F} \quad \vec{w}]$
$=\vec{r} \cdot(\vec{F} \times \vec{w})$
Standard 11
Physics
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