What is responsible for keeping an object at rest or maintaining an object's constant velocity? balanced forces external forces unbalanced forces Gravity Friction

balanced forces external forces

Explanation:

A body that is under a network of balanced external forces will experience no resultant force at all, since all the forces cancel themselves out. A body that is moving with this type of force will  experience no acceleration, since there is no force acting on them. This lack of acceleration means that the body maintains a constant velocity if it is already in motion, or zero when the body is at rest.

their crystal patterns have been disrupted by stress