Physical interpretation of the definition of torque :

1.	Physical interpretation of the definition of torque :
Answer» Solution :As shown in the figure a force `vecF` is acting on a PARTICLE P of rigid body. Force `vecF` is taken in the plane perpendicular to the axis of rotation. The axis is perpendicular to the plane of the figure and passing through point O. The position vector of P w.r.t. the centre of its CIRCULAR path is `VECR`. The angle between `vecF and vecr` is `theta`. To examine the effectiveness of the force in produing rotational motion, `vecF` can be resolved into two mutually perpendicular components. (1) Component of `vecF` parallel to `vecr` is `Fcostheta` which does not produce rotational motion. (2) Component of `vecF` perpendicular to `vecr` is `Fsintheta`. Which can produce the rotational motion. If F and/or `theta` large, `vecF` will be more effective. Moreover if the position vector `vecr` of the point of application of the force `vecF` is large, the effectiveness of the force in producing rotational motion is more. Thus the quantity responsible for producing rotational motion is not only `vecF` but `rFsintheta`. If can be written in vector FORM as under. `vectau = vecr xx vecF` Torque is the measure of effectiveness of force in producing rotational motion.

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