Question
Explain that torque is only due to transverse component of force. Radial component has nothing to do with torque.
✓
Answer
Torque is defined as the moment of force. 
$\tau=\vec{\text{r}}\times\vec{\text{F}}=\text{r}\text{ F}\sin\theta\ \hat{\text{n}}.\hat{\text{n}}$ is along axis of rotation. If a force $\vec{\text{F}}$ acts at an angle $\theta$ to the position vector i then $\text{F}\sin\theta$ acts perpendicularly to the position- vector. Therefor $\tau=\text{r}_{\bot}\text{F}$ and so the radial component does not bring any influence on the torque.
$\tau=\vec{\text{r}}\times\vec{\text{F}}=\text{r}\text{ F}\sin\theta\ \hat{\text{n}}.\hat{\text{n}}$ is along axis of rotation. If a force $\vec{\text{F}}$ acts at an angle $\theta$ to the position vector i then $\text{F}\sin\theta$ acts perpendicularly to the position- vector. Therefor $\tau=\text{r}_{\bot}\text{F}$ and so the radial component does not bring any influence on the torque.Need a full question paper?
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