If a force is applied to an object and the force is parallel to the motion, the resultant velocity of the object will depend on various factors such as the magnitude and direction of the force, the mass of the object, and the initial velocity of the object.
If the force applied is in the same direction as the object's motion, it will increase the object's velocity, causing it to accelerate. The resultant velocity will be greater than the initial velocity.
If the force applied is in the opposite direction of the object's motion, it will decrease the object's velocity, causing it to decelerate. The resultant velocity will be less than the initial velocity.
If the force applied is equal in magnitude and opposite in direction to the object's motion, the object will experience a net force of zero. In this case, the object will continue to move at a constant velocity, maintaining its initial velocity.
It's important to note that these statements are based on the assumption that no other forces are acting on the object and that there are no external factors such as friction or air resistance.