How can an object maintain a constant velocity but still have an unbalanced force?
You are applying a force to the object, yes. However, the ground is also exerting it’s own force on the block, tending to oppose the force you apply. This force is better known as friction. Eventually, as you keep increasing force, the object will suddenly jerk – this is an initial acceleration of the force you apply overcoming and being greater than friction. As you stabilise the force, friction will hold onto the object as much as you are pushing it, to balance the forces, so no net force exists, therefore no acceleration. However, the object would already be in motion (constant uniform) because you already overcame the friction. It will continue in this state of uniform motion until you push harder (acceleration because friction is now less) or stop pushing (friction is now more, so deceleration or negative acceleration). Hope this makes this clearer for you. Regards.
