In real life there is a static friction acting on the body that is stationary and a kinetic friction acting on the body in motion. Those two forces are usually not equal. There is a static friction coefficient that prescribes the static friction and kinetic friction coefficient that prescribes the kinetic friction.

In Gazebo, however, you can only set one friction. Moreover you put a friction to each of the link but the friction coefficient is defined for a pair of surfaces in contact. So how to set the physics of friction realistically?