LET'S PUT THESE POSTS IN MOTION!
Newton's third law creates the connection between action and reaction as it applies to forces being applied onto an object. It sets the basis to understanding what happens between an object and the force applied to it. It further can explain what happens when a person applies force onto an object (anything that has a mass greater than zero).
Formally stated, Newton's third law is: for every action, there is an equal and opposite reaction. This means that when a force is applied onto an object, the object will react by applying force back, to the same extent, in the opposite direction. For example, if a person pushes a wall, the wall pushes the person back with the same force in the exact opposite direction. This Newton's law is exploited for locomotion every day, several times a day.
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As a person pushes backwards and downwards on the ground, the ground pushes forward and upward, causing us to move forward. With out the implications and applications of Newton's third law of motion, we could not move forward. This is the exploitation of ground reaction forces. Another example is the ability to jump vertically, as we push downwards on the ground, the ground pushes back up to the same extent, helping cause lift.
Swimming is another possible example. As we push the water backwards or backwards and downwards, the water pushes back in the opposite direction to the same extent, propelling our body forward in the water (i.e. swimming). Now imagine a person on roller skates pushing a wall that will not move. Since the wall is going to push back in the opposite direction to the same extent, the person moves backwards.
Often, I am asked to explain how is Newton's third law of motion correct if there are surfaces that when we try to walk or run on, we cannot. Every time we try to advance on ice, slippery surfaces, and even sand, we find it challenging and definitely not as easy as on harder surfaces. The answer lies in the fact that if for any reason, the force we are trying to apply is dispersed, than lesser or no force is applied to the surface, thus surface reacts with little to force back, often not being enough to move us forward.
Slippery and less stable surfaces cause us to invest a significant amount of force sideways as we try to create stability, instead on pushing downward and backwards. The origin of this problem is in the fact that we cannot actually push straight down because of a mechanical lock in our ankle joint. Thus, we must "open" the mechanical lock first by rotating the foot outwards first, and only then we are able to actually push the ground.
Yet, slippery surfaces cause us to waste a substantial amount of energy in creating stability and balance of the foot at the expense of pushing the ground. We end up sliding and slipping instead of advancing forward. The less friction the surface has to offer, the more energy, force, and effort is wasted sideways rather than forward.
Unfortunately, Newton's third law of motion sometimes works against us, and can negatively influence our body. As we engage in movement and sports, we are often required to land on the ground or repeatedly apply extensive forces onto the ground. Immediately after, equal forces are applied to the body. This bears the potential of injury if the reaction forces are greater than any of the body's tissues ability to withstand them. These can include trauma to tissue, fractions, and more.
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