Answer & Explanation:
If the resultant force is zero, a moving object towards the right will stay at the same speed. If there is no resultant force then a system is said to be in equilibrium.
If the resultant force is not zero, due to a force towards left of a moving object will slow down - depending on the direction of the resultant force:
it will speed up if the resultant force is in the same direction as the object is moving
it will slow down if the resultant force is in the opposite direction
Please note that the object could also change direction, for example if the resultant force acts at an angle.
