Newton's First Law of Motion
“An object at rest remains at rest, and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force.”
Have you ever tried to push a parked car with your hands? That is definitely not an easy task. It would be equally difficult to stop a moving car with your hands. Simply, that is all Newton’s First Law says. In other words, a force is always needed to move an object that is at rest and a force is always needed to stop an object that is moving. This tendency of objects to resist motion is called inertia. It is measured as the mass, of objects.
You may have noticed the phrase “unbalanced force.” That phrase stresses that a force cannot move nor stop an object if it is being balanced by another force. Imagine you pushing on a door to close it and a friend pushing on it from the other side to open it. At one point the force you apply will be balanced by the force your friend is applying, and the door will remain as it is. Simply put, when you balance a force you cancel its effect.
Balanced and Unbalanced Forces
It is important to identify whether forces are balanced or unbalanced to apply Newton’s laws. Balanced forces always cancel the effects of each other. Therefore, when forces are balanced, there is no change of motion. An example for balanced force is a boat which is floating on water. Here, the weight of the boat is balanced by the upthrust from the water. An object can be at rest even when forces are acting on it, as long as the forces are balanced. It can be moving at a constant velocity too.
When the force applied in one direction is greater than the force applied in the opposite directions, that force is unbalanced. In a game of tug of war, one team will win because of these unbalanced forces. If the forces exerted by both the teams are equal in magnitude, the rope will not move. However, when the force exerted from one direction exceeds the other, it will create an unbalanced force causing the rope to move towards that direction.
