According to Newton’s third law of motion, “To every action, there is an equal and opposite reaction.” This means that whenever an object interacts with any other object, there exists a pair of interaction forces acting on both objects. The third law of motion is also called the action-reaction law. Both the action and reaction forces act on the objects simultaneously. If both the forces are equal in magnitude, equilibrium is maintained, and the object does not move. In such a case, a balanced force is said to be existing. If one of the forces is greater than the other, the object is subjected to motion, and an unbalanced force exists. Newton’s third law of motion is also known as the law of interaction.
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Examples
1. Recoil of a Gun
The recoil of a gun is one of the best demonstrations of action-reaction forces. When a bullet is fired from a gun, the gun moves backward. The action force exerted due to firing is in a forwarding direction that causes the bullet to move ahead. The jerk felt on the gun that pulls it in the backward direction exists due to the reaction force. This is the reason why a person operating a gun takes the support of his shoulder to avoid injury.
2. Swimming
A person swimming in a forward direction pushes the water in the backward direction with his/her hands. This force applied by the person acts as the action force, which leads to the generation of a reaction force. This pair of forces, acting together simultaneously on the person’s body and the water, causes the person to swim in the forward direction.
3. Pushing the Wall
When a person sitting on a chair pushes the wall with his feet, the chair moves backward. The motion of the chair can not exist without the existence of a force. Therefore, the force responsible to move the chair is the reaction force. The reaction force is always exerted in the direction opposite to the direction of the action force. Hence, the chair moves in a backward direction.
4. Diving off a Raft
When a person jumps out of a boat and steps on the bank, the boat moves back in the direction opposite to the direction of the jump. The force applied by the person on the rigid surface of the ground is the action force. In contrast to the action force, a reaction force gets generated that pushes the boat and causes it to move.
5. Space Shuttle
When a rocket is ignited, a series of chemical reactions take place that generate a huge amount of gases. These gases when hit the ground cause a force that helps the rocket to move upward. A similar process occurs in the jet engine. The only difference is that the rocket is required to carry an oxidizing agent because it has to enter an environment that does not contain oxygen.
6. Throwing a Ball
When a ball is thrown on the floor or a wall, it bounces back. The force exerted by the ball on the ground or wall is the action force. The force that the ground or wall exerts on the ball in response to the action force causes the ball to jump or bounce back. This force is nothing but the reaction force.
7. Walking
When we walk, a significant amount of force and pressure is exerted on the ground by our feet. The ground in response exerts an equal amount of force in the opposite direction. In absence of the reaction force produced by the ground, our foot sinks. Similarly, if the action force supplied by the foot of the person is significantly higher, the reaction force can help us to jump. Hence, walking is possible because a pair of action-reaction forces act on the feet and the ground.
8. Hammering a Nail
While hammering a nail in the wall, a force is felt on the person’s hand who is holding the hammer. It gets developed as a result of the force applied by the person on the nail. Both the forces are directly proportional to each other, which means with an increase in the action force, the reaction force increases.
9. Jumping
A person jumping on a hard floor gets hurt more severely than a soft surface. This is because the weight of the person causes an action on the surface. The surface, in turn, generates a reaction force that acts in the opposite direction. The hard surface does not absorb any force and generates the same amount of force in response. On the other hand, the soft surface that is elastic in nature absorbs a significant portion of the action force and therefore, generates less reaction force.
10. Evacuating a Balloon
A balloon filled with air when released with its end untied lets out air with force. With the help of the action force that is caused due to the air rushing out of the balloon, a reaction force gets developed that causes the balloon to move upward.
Your explanation is kind of abstract. It should be so that one can see that the reaction force is a force :
1) Jaw exerting force back on fist; we do see that the fist applies the force on jaw as it causes pain to it. But we do not see the way the corresponding reaction force reacts. And you pull out the law for explanation, saying it must be like that. This is why your explanation is abstract. A concrete proof of your explanation would be : “… and that is that reaction force which causes pain to the fist”. And also because you like to say something more, to put “If both the forces are equal in magnitude, equilibrium is maintained, and the 2 objects [not “the object does not move] do not move”, you should also explain clearly by saying like this “If both these 2 forces are not equal, then the jaw will not stand still, but get displaced backwards” and also “if these 2 forces are equal, but if the hardness of the jaw is less than of the one of the fist, then even the jaw does not move, but it will get cracked, broken”.
2) You put : “The jerk felt on the gun that pulls it in the backward direction exists due to the reaction force”. But how this reaction force is exerted? So, you need to explain clearly, instead of simply saying that by basing on the Newton’s law, so that one could grasp the real meaning of the reaction force, not just have an abstract idea about it.
Tentatively, you need to say something more, like : it is the expanding gas converted from the the gunpowder when ignited, that forces the bullet out at an extreme speed. It is this force that causes the reaction force – the recoil force transferred to the gun.
3) You put : “A person swimming in a forward direction pushes the water in the backward direction with his/her hands. This force applied by the person acts as the action force, which leads to the generation of a reaction force”. But the reaction force from where? You need to say more : from the water.
And you put “This pair of forces, acting together simultaneously on the person’s body and the water, causes the person to swim in the forward direction”. But if the volume of water is, say just a couple of times more than the body of the swimmer, then what will happens? The standstill of the swimmer body. So, while acting together, the water volume must be up to a magnitude so that its reaction force is greater than the one exerted by the whole body in movement of the swimmer on it.
3) Pushing the wall.
You put : “Therefore, the force responsible to move the chair is the reaction force; The motion of the chair can not exist without the existence of a force.”. But, if the person doesn’t push with hard enough force, then the chair will … not move at all. So, you need to say more, something like : the wall exerts a reaction force on the pushing hand – that is why there is a feeling of pressure, of pain on the 2 hands – and this reaction force must be greater than the one exerted by the 2 hands. If this reaction force is of a lesser, then the wall will collapse. And because this reaction force is greater than the applied force, so the chair moves backward. A clearer explanation : suppose the wall is put on wheels like the chair, so that it can move backwards and forwards, just like the chair. So, what happens when that reaction force exerted by the wall is lesser by that applied force exerted by the person? It then will move backwards; the wall moves, not the chair. And because you like to use the person sitting on a chair as example, you need to say more : as there is another force that is involved here, the friction force against the wheels …
4) …
… up to 10)
In brief, your introductory explanations to this matter are not clear-cut enough, kind of more or less abstract.
(Please note : there are certainly some errors here and there, about the physical or grammatical aspect of what I put in words, as I don’t recheck it; as my objective is just to give you an idea of what is a thorough, a clear explanation. And it’s better to have fewer examples [say 5] with clear-cut explanations, than to have many examples [say 10, like here] but with quick, superficial explanations).