How to calculate the torque is the formula you wrote. It should be noted that, firstly, L is the distance from the line of action of F to the axis of rotation (the distance from a point to a straight line in mathematics). Secondly, the clockwise and counterclockwise effects of torque on the rotation of objects are different. The sum of moments of all forces must be specified as positive in advance, and the sum of all forces is algebraic sum.

The physical meaning of torque: changing the rotating state of an object. If the object is stationary or rotating at a uniform speed, it is said that the object is in a state of rotational equilibrium (angular velocity is constant), and the corresponding resultant torque is zero; If the resultant torque is not zero, the angular velocity of the object will change, and we say that the rotational state has changed. In this sense, according to Newton's second law, it can be understood that the resultant torque is the reason why an object changes its rotational state.

In middle school, most of them talk about rotational balance. At this time, there is a rotational balance condition: the resultant torque is zero.