question_answer

  An object experiences a net zero external unbalanced force. Is it possible for the object to be travelling with a non-zero velocity? If yes, state the conditions that must be placed on the magnitude and direction of the velocity. If no, provide a reason.        [NCERT]

Answer:

                  Yes, it is possible for the object to be travelling with a non-zero velocity, if it experiences a net zero external unbalanced force. This is due to inertia of motion. If body is initially moving with some velocity on a smooth surface, then it will continue to move with same velocity, though the net external force acting on the body is zero. For example, when we stop pedalling a moving bicycle, the bicycle begins to slow down and finally comes to rest. This is again because of the friction forces acting opposite to the direction of motion. The force of friction opposes the motion of the bicycle. If there were no unbalanced force of friction and no air resistance, a moving bicycle would go on moving forever.