An object will continue to travel at a constant speed unless acted on by an unbalanced force, and for every force acted on there is an equal and opposite reaction in the other way. So, the speed and direction of the object will be changed.
An unbalanced force acting on an object will cause it to accelerate, changing its state of motion. This occurs because the net (resultant) force is not zero, leading to a change in speed or direction. Newton's laws of motion explain this relationship between force and motion.
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