A person throws an object on a horizontal frictionless plane surface. It is noticed that there are two forces acting on this object—(i) gravitational pull and (ii) normal reaction of the surface. According to the third law of motion, the net resultant force is zero. Which one of the following can be said for the motion of the object?

According to Newton's first law of motion, an object will continue in its state of rest or uniform motion in a straight line unless acted upon by an unbalanced net force. In the given scenario, the object is on a horizontal frictionless plane where the only vertical forces are the gravitational pull and the normal reaction. Since these two forces are equal and opposite, the net resultant force acting on the object is zero. Newton's first law states that when the net external force is zero, the object's state of motion remains unchanged. Therefore, if the object was already thrown and is in motion, it will continue to move with a constant velocity, meaning both its speed and direction remain unchanged. This is often referred to as inertial motion.