Question

In case of a planet revolving around the sun, the torque is
A) Zero
B) Maximum
C) Minimum
D) Depends on the shape of the orbit

Answer 1

Hint:
Rotation: It is defined as a circular movement of an object around a center (or point) of rotation.
A rotation axis is defined that the three-dimensional body can always be rotated and about an infinite number of imaginary lines.
If the axis passes through the object's center of mass, the object is said to rotate upon itself, or spin.
Rotation around an external point, e.g. the planet Earth around the Sun is an example of a revolution or orbital revolution when it is produced by gravity. The axis is called a pole.
Revolution: The motion of an object around another object or a center of mass.
A single complete cycle of such motion.

Complete step by step solution:

Torque: It is defined as the rotational equivalent of linear force. It is also referred to as the moment of force, rotational force, or turning effect, depending on the field of study.
Torque can be defined as a twist to an object around a specific axis.
Torque is calculated as the product of the magnitude of the force and the perpendicular distance of the line of action of a force from the axis of rotation.
\[\tau = {\text{r x}}F\]=$\tau = |{\text{r| |F|sin}}\theta $, here $\tau = $ torque vector produced, \[r = \] position vector, \[F = \] force vector, \[x = \] cross product, $\theta = $ angle between force vector and level arm vector.
The gravitational attractive force acting between the planet and the Sun is along the radial vector and therefore, the angle between the force and the radial vector is zero.

Hence the correct option is (A).

Note: In three dimensions, the torque is a pseudo force; for point particles.
It is formulated by the cross product of the position vector (distance vector) and the force vector.
The magnitude of torque of a rigid body depends on three factors: the force applied, the angle between the force and lever arm vectors, and the level arm vector connecting the point about which the torque is being measured to the point of the force application.