Forces affect how objects move. They may cause motion; they may also slow, stop, or change the direction of motion of an object that is already moving. Since force cause changes in the speed or direction of an object, we can say that forces cause changes in velocity. Remember that acceleration is a change in velocity. Let’s say an object is moving along a table on earth, suddenly the finite table ends, resulting in the object being present in the air, which means there is no normal contact force N to combat the force by gravity mg, which is why there is an acceleration downwards. This proves as a projectile motion since the direction of motion start changing from horizontal to vertical. Another example is one throwing an object up. It moves up and slows down, reaching its maximum point, leading to it starting to move downwards. This too is a change in motion.
Unbalanced force is the change in direction of motion.
Here, look at the following definition: If two individual forces are of equal magnitude and opposite direction, then the forces are said to be balanced. An object is said to be acted upon by an unbalanced force only when there is an individual force that is not being balanced by a force of equal magnitude and in the opposite direction.
