Newton’s fist law of motion states that an object in motion tends to stay in motion and an object at rest tends to stay at rest. This is due to inertia. Inertia is the want of the object to not change its motion. The more mass an object has, the more inertia it has. If the object is moving, it still has inertia and still does not want to change its motion. Even in a gravity free area (like outer space) an object with more mass will be harder to change its motion because of inertia. If there was no outside force, then the object would not change its motion and it will remain in equilibrium. This means the object is not accelerating, and could be moving at a constant velocity or sitting still.
            
If a ball is sitting at rest, it is not moving and is reluctant to changing its motion. The ball does not have much mass so its inertia is not very strong. But if you push it in a friction free environment, the ball will move and be reluctant to changing its motion. If the was much bigger and had more mass, the inertia would be greater and take a much stronger force to change its state of motion. Plus if it is sitting still then it is at equilibrium. If the ball were to be pushed and there was no friction, then it would be at equilibrium.