Question

The stone of hand flour grinder is provided with a handle near its rim. Give a reason.

Answer 1

Here we have to apply the concept of moment of force:
A force's moment is a measure of its ability to cause a body to spin about a single point or axis. A moment is due to a force that does not explicitly have an equivalent and opposite force in the action line.

Complete step by step solution:
A force's moment is a measure of its ability to cause a body to spin about a single point or axis. This is distinct from the inclination of a body to shift in the direction of the impact, or translate. The force must act upon the body in such a way that the body may continue to twist in order for a moment to grow. When a force is exerted such that it does not travel through the body's centroid, this happens.

The amplitude of the moment of the force acting on the point or axis is directly proportional to the distance between the point or the axis and the force. It is defined as the product of force and the arm of the moment. The moment arm or lever arm is the perpendicular difference between the force line of operation and the moment centre.
By combining the magnitude of the force with the perpendicular distance between the point and the line of action of the force, we can find the magnitude of the moment.

Hence, in order to achieve the greatest turning effect, the handle is positioned at the rim such that the full perpendicular distance of the lone action of the force from the axis of rotation is obtained.

Note: A rotation around the centre of moments in the clockwise direction is called a positive moment; a rotation around the centre of moments in the counterclockwise direction is considered negative.