Newton’s Third Law of motion as it applies to Space Rails
At last, we come to the law that is quite easy to memorize and as usual, quite easy to understand. This law relates to motion in a manner that is slightly different from the others. The force seems to place more emphasis on balance rather than movement. Before any coordinated movement can occur, balance must be first achieved.
What the law says
‘For every action, there is an equal and opposite reaction’
Forces occur in pairs. It’s the reason why we are able to stand on the Ground without actually sinking in, it’s the reason why you sit down on a chair and the chair doesn’t collapse. Every force you can think about involves the interaction of two objects. One object exerts a force and the other responds with an equal amount of force. So, when you stand on the ground or sit on a chair, the ground or chair, as the case may be, exerts an upward force on your body that is equal in magnitude to the downward force exerted by your weight. It's easy to see why a chair that is no longer strong enough could crumble under your weight when you sit on it.
If you have ever wondered why you cannot walk on water, your answer lies in the Newton’s Third Law of motion. As mentioned earlier, when you stand on the ground, your body exerts a force that is equal to your weight. This force acts downwards. In response, the earth exerts another upward force that counteracts your weight. Water is not able to exert the same force as the earth so it cannot counteract your wait. That is why you see yourself sinking when you try to stand on water. But if you place a small object, say, a kite on the same body of water, the kite would float. This is because the magnitude of the kite’s force (or it’s weight) is not more than the reaction force exerted by the water.
If we are to look at the spacerail example, you would notice that the rails are made of flexible metal sheets and the marble is quite light. Thus, the force exerted on the rails by the weight of the marble is almost negligible. This accounts for why the marble is able to balance and move on the rails. If you were to put a much heavier object, say a shot-put, the rails would no doubt crumble under this weight. This is because they are unable to counteract the effect of the force exerted by the shot-put.
The series has tried to present the concept of motion in an easily relatable way. Remember, the concept of motion comes to life around us and it is an idea you can easily relate to. And of course, you can keep building your space rails to bring the concept even closer. As you move up the levels, the journey becomes even more exciting.