Importance of Physics to Mankind
In our world, everything exists for a purpose. The tree that grows, the volcano that erupts, formation of rainbow and aurora, from the planets surrounding the sun to a tiny atom in glass of water, every phenomenon can be described and explained through the laws of Physics. Physics (Greek: physis – φύσις meaning "nature") is a natural science that involves the study of matter and the world. Archimedes (Ἀρχιμήδης) (287 BC – 212 BC) is one of the earliest founders of physics; he introduced the law of flotation (buoyancy) through his “Golden Crown experiment” where he discovered the purity of gold in the king’s crown, after that many other scientist came out with other brilliant ideas, Ptolemy (90 AD – 168 AD), Sir Isaac Newton (1643-1727), Albert Einstein (1879 -1955) and others more.
Physics exists and applies in every part of our life, but if only we take notice then only we can realise that there are the forces around us. So in the human body, physics applies here is that our body limbs are actually levers. Levers are planks with load and effort applied to it against a fulcrum. Three classes of levers are there, Class I, Class II, and Class III. Class I and II are good because they need less effort to lift a heavy object, in our body the head is the Class I lever and the leg is the Class II lever, then it need little muscle effort to lift the heavy head and heavy body during tip – toeing. Class III on the other hand produces large distance with speed although it requires more effort. Class III example is the hand, the hand is required to do many things so it is very suitable to be a Class III lever.
Then it goes to the pulley, a pulley is a string attached to a pulley which is a fulcrum like thing, one end of the rope is the load and the other ends it the effort. The advantages of pulleys in our body are to change the direction of force because it will be more convenient for the muscles to pull up the limb, for example if the leg wants to perform extension at knee joint, the muscle has to contract upward, so it is not possible to extend the leg during sitting posture. That’s why we need pulleys to change the direction of force so that when we sit the muscle will contract horizontally and through the pulley at the knee, extension can occur. Besides that, it can increase the range of motion; normally a muscle can lift limbs up from a maximum of 90°, but with the pulley it can lift a limb above that from up to 165°. So it is an advantage to have a pulley system in our body. The knee joint consist of the quadriceps tendons and patella, these two functions as a rope and a pulley.
These physics applies from the internal force of the body, there are also external forces acting on the body. One example is the buoyant force in water; Archimedes states that any object is immersed into the water will face buoyancy depending on how much of water is displaced by that object thus reducing the weight of the object. So if the human is immersed in the water, he will experience weight loss and that brings about many benefits. Since you’re lighter in water, joints receive less pressure from the body’s weight and movement is feasible. Patients recovering from muscle injury or coma are asked to do exercises in water and good flexibility means good recovery. Due to the hydrostatic pressure of water, patient recovers from swelling as well. Pressure is applied evenly over the swollen part in all direction, and improves circulatory of blood and stagnant body fluid.
The water plays another important role which is to maintain that persons balance, during exercise that person may trip and crash on the floor, this is dangerous as the old wound may open up and at the same break other bones too. Viscosity of water is high due to the hydrogen bond in water (Cohesion force). So this causes friction and it slows that person down if he falls. The water also improves overall muscle shape and strength because it gives an overall resistance, so even a simple action of abduction requires all the muscles of the arm to work together.
The earth we live in pulls us onto the ground and do not let us escape to the space. This force is called Gravity; gravity is the gravitational force between the earth and its occupants. This also influences our muscle; body weight is dependent on the centre of gravity of a person, so if the COG falls out of the base of support, then the person will fall. So in order not to fall, that person has to use muscular force to balance back and stay within the base of support. Not only that, since gravity pulls everything down, therefore a person can build their muscle by lifting weights.
Physics not only applied in the musculoskeletal system, but also in the respiratory system. When we respire, we take in oxygen from the atmosphere, and then the oxygen enters the lungs and to the alveoli, from there oxygen diffuse into the blood and it is carried to our respiring cells. These are normal process of the body however; external environment can affect the respiratory system.
There are three laws about oxygen diffusion into the blood capillaries; Henry’s law states that, “when a gas is in contact with the surface of a liquid, the amount of the gas which will go into solution is proportional to the partial pressure of that gas”, which also means the concentration of a particular gas in the atmosphere. So oxygen more in the air compared to carbon dioxide and other gases, therefore the oxygen is more likely to diffuse into the blood.
Graham’s law states that, “when gases are dissolved in liquids, the relative rate of diffusion of a given gas is proportional to its solubility in the liquid and inversely proportional to the square root of its molecular mass”, which means the rate diffusion is dependent on the solubility and the size of the molecule. Comparing oxygen and carbon dioxide, carbon dioxide’s solubility is higher in the blood compared to oxygen. At the same time; oxygen is smaller in size compared to carbon dioxide makes it easier to diffuse. Therefore diffusion rate of oxygen is equally same as carbon dioxide in the blood and gaseous exchange can occur smoothly.
Fick’s law states that, “The net diffusion rate of a gas across a fluid membrane is proportional to the difference in partial pressure, proportional to the area of the membrane and inversely proportional to the thickness of the membrane”, which also means the diffusion of gases are affected by the surface area for the diffusion to take place and the thickness or distance for the molecule to go through. The wall of alveoli is extremely thin to minimize the thickness and distance for the gas molecule to pass through to the artery, and the unique grape shape of the alveoli allows a large surface area for gas exchange to take place.
Then it comes to the atmospheric pressure,atmospheric pressure decreases with altitude, or the height above of sea level. This is caused by the weight of the column of air above it causing compression to the air below and therefore the air pressure at sea level are normally higher. At higher altitudes, the density and temperature of the air are lower; as a result, the frequency of collisions of the molecules is decreased causing low air pressure. Air pressure can be measured using a barometer.This applies to humans especially at the lungs. The intercostals muscles work together with the diaphragm increasing the size of thoracic cage causes air pressure in lungs decreases, the air moves in down the pressure gradient and exchange of gases occurs. That person may suffer illness such as nausea or lack of breath due to the low atmospheric pressure. We then have to increase our breathing rate to cope with this new environment.
The summary is that the human body not only functions physiologically but is also influenced by the external environment. Like our hands and legs are unexpectedly levers and pulleys, we wouldn’t notice that unless we take a closer look at our body. Life creation is amazing because, due to the world our body has evolved to cope with these changes, like balancing off an uneven surface, and even improving the respiratory system when we are at high altitude for example. Since at high altitude there is less oxygen, our body then speeds up our respiration to ensure all the respiring cells in our body get sufficient oxygen. Therefore, knowing all the law and forces of physics, we can know how to avoid danger and using it to simplify our life which is an advantage. We can manipulate physics to do new things, for example building hydroelectric dam to produce electric, the unique aerofoil shape of the wing of the plane and others. So it is important to pay attention to these forces in our world.
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