The torque on a planet about the centre of th | vedclass

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(A) The gravitational force exerted by the Sun on a planet acts along the line joining the Sun and the planet. Let $\vec{r}$ be the position vector of

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(A) The gravitational force exerted by the Sun on a planet acts along the line joining the Sun and the planet. Let $\vec{r}$ be the position vector of the planet with respect to the Sun and $\vec{F}_g$ be the gravitational force acting on the planet. The torque $\vec{	au}$ is given by $\vec{	au} = \vec{r} 	imes \vec{F}_g$. The magnitude of the torque is $	au = r F_g \sin 	heta$,where $	heta$ is the angle between the position vector $\vec{r}$ and the force vector $\vec{F}_g$. Since the gravitational force is a central force,it acts along the line joining the centers of the two bodies. Therefore,the force vector $\vec{F}_g$ is directed towards the Sun,which is opposite to the position vector $\vec{r}$ (i.e.,$	heta = 180^{\circ}$). Since $\sin(180^{\circ}) = 0$,the torque $	au = 0$.

The torque on a planet about the centre of the Sun is ..............

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