What always happens to the motion of an object when unbalanced forces act on it?

Answer 1

There's no such thing as "an unbalanced force".

When the group of forces acting on an object is unbalanced, then the object

accelerates, in the direction of the vector sum of the forces.

Answer 2

The object accelerates in the direction that the greater force is pushing or pulling it.
any object is acted upon by an unbalanced force will make the object move with the unbalanced force as there is not the right amount of the other force to stop it.
if they were balanced forces the object would find equilibrium and would end up basically being held in one place, or travel on one vector without changing course.

As for an object under the effect of unbalanced forces? It would NOT behave like the one described above. that is all that could be said.
The object accelerates in the direction of the 'net' force ... the vector sum of all

of the individual forces. The rate of acceleration is proportional to the magnitude

of the net force.
It (the motion) is changed.

(Your last it being the object ... I hope).
when an unbalanced force act on a moving object, the velocity of the object will change.
When an unbalanced force acts on an object, the object will accelerate. This is a fundamental law of physics that goes back to Newton. Further, the object will move in the direction of the unbalanced force.

We know that force is equal to mass times acceleration (F = m x a). If force is applied, the object is accelerated in the direction that the force moves it. If force increases, the object will accelerate more because acceleration must also increase.
There's no such thing as "an unbalanced force".

When the group of forces acting on an object is unbalanced, then the object

accelerates, in the direction of the vector sum of the forces.

Answer 3

it will cause a change in motion