The perpendicular distance between the applied force and the center of rotation is called the

Lever arm is defined as the "perpendicular distance that exists from the rotation axis to the line of action of the force". Being its magnitude related to the application of the force that produces a torque.

To understand it better:

The lever arm is an effective distance to apply a force with respect to a certain point, and this distance serves as an effective applied force amplification factor.

So, the greater the lever arm, the greater the torque and the lesser the force we have to apply.

the rearrangement of particles in a physical change. hope this