Nov 7, 2019 in Research

To What Extent Did Newton’s Law Of Motion Contribute To The Construction Of Bridges?

Isaac Newton was born on December 25, 1642. He was born prematurely. It never occurred to those around him that Newton was a genius. Newton was intelligent and very thorough in everything he was doing. His scientific achievements have dominated philosophy and science for two centuries. Newton’s power of concentration enabled him to accomplish his scientific achievements in a short time, which can be attributed to how brilliant he was. Newton carried on the work of Galileo, formulated, and concluded the needed physics laws. Galileo was also physics pioneer. Galileo emphasized the magnitude of acceleration through his study of motion, which laid mechanics foundation. It was upon Newton to ascertain mechanics as a precise science, therefore, stating the three laws of motion.  These laws are crucial in the construction of bridges applied by engineers. The bridge is held up by the force exerted by the object weight and reactions the bridge support gives, according to Newton’s law of motion. The main aim of this essay is to discuss the extent to which Isaac Newton’s laws of motion contribute to the construction of bridges. To this end, the essay describes the application of Newton’s laws of motion in the construction of bridges, Newton; achievements, and the construction of bridges before and after the laws of Newton. 

Application of Newton’s Laws of Motion in the Construction of Bridges

Our daily lives depend a lot on availability of bridges.. Bridges can have the simplest form of a log that helps in crossing small ditches, or can be as complex as highway overpasses and spanning large water bodies. A bridge with busy traffic is built with a strong support to manage its dead weight and the load its carries. The three Newton laws of motion are vital in the construction of bridges. These Laws include Newton’s First, Second and Third Laws. The First law states that an object at rest will remain at rest unless acted upon by an outside force, whereas an object in motion will stay in motion unless acted upon by an outside force. In this respect, a bridge will stop unless an external force is exerted. In order to understand the First Newton’s law mathematically, his Second law is essential. Newton’s Second law argues that a force is equal to its mass multiplied by its acceleration (Fnet = ma). This law claims that when force applied to the bridge accelerates in the direction of that force, at zero force, the bridge will not move, and it will be in equilibrium. Given that, bridges have no horizontal motion hence vertical acceleration or the gravity force. 

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The Third Newton’s law states that there is an equal and opposite reaction in every action. A car on a bridge exerts a force on the bridge amounting to the force exerted on the car by the bridge; therefore, when the bridge is in equilibrium, there be will zero force. In order to understand how a bridge works it is important to consider the three Newton’s laws. Other than the forces exerted by the traffic and people, also known as live load, two other forces occur. These forces are compression and tension forces; these forces make the bridge compress and stretch respectively. 

Most bridges encounter these forces – compression and tension. In areas at the bridge where many people pass, it experiences both forces. In the upper part, it bends due to compression, and at the lower part of the deck it stretches because of the live load weight. Bridges are supposed to handle the different forces their live loads impose on them. Two methods can help counter the situation. They include, transferring forces from weak points to areas resilient enough to manage the increased force, and distributing these forces all over the structure to equalize the excessive forces. Bridges are designed in five ways: cable-stay, suspension, truss, arch and girder. These designs have both disadvantages and advantages.

Girder Bridge is simple construction built with two simple supports. Girder Bridges are found in the eastern part of North Carolina. Girder Bridge encounters the two forces compression and tension on the upper and lower fraction of the decks. Arch bridges, although not commonly used, are a perfect weight disperses. An arch bridge has only compression force present that is essential when securing the bridge foundation that is needed for its stability. Spanning rivers and valleys best suite arch bridges because they cannot endure horizontal motion. An example of an arch bridge is shown in figure 1 below.

Truss is another bridge designed in triangular form effective in transmitting loads. Although these bridges might be structurally weak, their strength can be increased when several triangles are incorporated. Truss bridges can hold heavy masses. They are also pocket-friendly considering the materials used for its construction. Truss bridge dispenses its loads using the triangular shaped sections. Tension force is exerted on the lower part of the deck while compression force occurs on the upper side. 

Suspension bridges are unique because they use few supports and can cover large distances, mostly used in areas with deep waters, and high shipping traffic. The deck of a suspension bridge hangs from many lesser cable supports, which is under tension force. In addition, two major cables that run the entire length of the bridge are also under tension. Normally suspension bridge has two tower supports under compression. In order to uphold their tension, main cables are anchored at the end of the bridge. The diagram below shows the forces in a suspension bridge.

Cable-stay bridges are similar to suspension bridges. Cable-stay bridges are supported by cables from above that are connected to support towers. Cable-stay bridges are complex with the main tower directly connected with lesser support cables, instead of the main cable that connects to the towers. The road deck and support towers are under compression while support cables are under tension. The weakest deck parts make the bridge stronger. The balancing of compression and tension forces is possible if the bridge span in each section is compressed against the surface of the neighbouring segments, failure to do that leads to disruption of these forces. 

Bridge designers not only need to consider the expected forces, such as live and dead loads, when planning, but should also consider forces from outside, such as resonance-bridge’s enemy, weather and fatigue. Nature can be more powerful and challenging for a bridge engineer. Large water bodies crossways bridges making them vulnerable to powerful storms like nor’easters, hurricanes and typhoons and earthquakes. External forces alleviate structure weight and aerodynamics through careful concentration. Effects of wind can be reversed when the bridge decks are heavy; nevertheless, a lighter deck can survive an earthquake. Japan is often hit by major earthquakes. Therefore, such large-scale bridges are designed there, for example, the Akashi-Kaikyo suspension bridge. Wind speeds also cause a bridge to resonate. Resonance happen when stimulus make a frequency adjust with the natural frequency of another object. Increasing magnitude will be experienced due to affected object. Resonance sometimes leads to destruction, in cases such as the Tacoma Narrows Bridge. 

A bridge can be built with dampeners in order to prevent run off resonance. Dampeners keep the bridge from escalating because they limit the resonance to a section of the bridge. The collapse of Minneapolis Bridge the1-35W Bridge, in August 2007, led to bridge fatigue. Since any structure can pose fatigue, cautious bridge design and maintenance can moderate the bridge fatigue. A premature fatigue can be prevented when engineers design bridges that distribute their forces equally in the construction, thus preventing a side of the bridge from dealing with excessive force.

The Achievements of Newton and His Life

Newton  received his preliminary education in Graham’s King’s School. In 1661, he joined Trinity College in Cambridge. It was during this time in Cambridge that Newton’s interest in astronomy, optics, mathematics and physics developed. His interest in advanced science grew despite the fact that he was taught standard curriculum. Most of his time he spent reading modern philosophers’ works. In the year 1665, the plague stroked the college that led to its shut down. During this time of interruption from studying, Isaac Newton worked on strengthening his theories on law of gravity, optics and calculus. He also discovered the generalized binominal theorem and started to develop a mathematical theory, which later turned out to be infinitesimal calculus.

Over the years, Newton has been studying optics, examining the refraction of light using a glass prism. After a series of experiments, Newton came to conclusion that light was composed of particles and colour is an intrinsic property of light. Newton concluded that already collared light interacts with objects to produce colour unlike the objects that generate the colour themselves. This was called Newton’s theory of colour. In 1668, Newton built a telescope to prove his theory of colour that was called Newtonian telescope.

In 1679, Hannah Ayscough, Newton’s mother died. Newton took some time away and withdrew from all kind of academic associations. It was at this period that the theory of gravitation and its effects was developed.  He established that the relationship between a sling and pendulum, motion of moon and the falling of an apple from a tree is determined by a single force. In 1687, Newton published his first book on gravitation and mechanics theory, titled Philosophiae, Natrulis, Principia Mathematica. It was the first book edition set for science of mechanics foundation. Newton further explained that the motion of the celestial bodies was controlled by gravitational force.

Later Newton proposed the three laws of motion. The first one stated that a body would stay still unless an external force is exerted to it. The second states that a change in motion is proportional to the applied force that is equal to acceleration multiplied by mass.The third states that there is equal and opposite reaction in every action.

After publishing Principia, Newton was considered the most famous in the circle of science. His discoveries were among greatest achievements in the history of humanity. This made him be extensively recognized. His confidence increased with fame that built up his interest in undertaking other specialties. He became more active in public life, hence losing interest in the Cambridge position. This resulted in him being elected to the Parliament as Cambridge representative. With time Newton’s life circle extended, he associated with political theorist. One of them was John Locke. During this period, upcoming generation of British scientists were amazed by the work Newton was doing and pictured him as their leader.

Newton suffered yet another breakdown and came out of it with a complete loss of interest in scientific discoveries. He spent most of his time studying prophecy and alchemy. Newton was later appointed as warden of the mint in the year 1696.  Later he went to London where he achieved governmental position that he so much desired. Few years later after his appointment as mint warden, he was promoted to mint master in 1699. He worked hard to improve the currency rank by punishing counterfeiters and clippers. This worked as it pushed the currency level from silver to gold. He held this position until his death.

How Engineers Build Bridges without Newton’s Laws and after

Industrial revolution originated from machines like cars, buildings, roads bridges, which all owe it to Newton’s Laws. Before that engineering was a disorganized activity characterized by guesswork and rules of thumb. Long before mortar was invented, bridges were built as a simple structure for easy accessibility. Simple resources were used such as stones, dirt and wooden logs. This enabled them to access only close and short distances. In early time, a log was thrown across a watercourse or even two ropes were tied across. They tied rope’s up and lower end that helped when crossing the bridge, for the upper one would offer support while walking. As time went by, stone structures were introduced and materials such as bricks and stones were used. First modern bridges were built by the Romans. Many of them are still standing. 

During the Middle Ages, bridges were built with heavy piers crude stone arches. They helped manage water traffic. New England covered bridge was one of the early American designs. Trained masons were not required since wood was cheap and plentiful. In 1779, bridges were built out of wrought iron and cast, though they were of low tensile strength. These kinds of bridges were built by different engineers, such as Victoria Bridge in Montreal. In 1850, another was built in Menai Strait in North Wales. Suspension bridges are commonly used in the 21st century because they cover longer distances. Industrial revolution brought about modern bridge technologies. Steel replaced iron, when constructing bridges with an aim of supporting large masses. This has led to construction of many different bridges with several designs. In 1889, the bridge was constructed below the Niagara Falls; it was an arch bridge covering 840 feet. It was constructed out of steel. 

As the 19th century ended, concrete was combined with steel to construct Concrete Bridge, the 1st one was completed in 1898. Tunkhannock Creek Viaduct in the U.S.A is the largest concrete bridge, covering 2,375 fee. Modern bridges are commonly designed using architectural software and computers before construction. As time progresses, technology also advances, thus, building techniques will not be left out. Bridge construction will progress further as old materials will be replaced by new materials.

Conclusion

Newton’s laws of motion are evidently essential in bridge construction. The First law states that an object in motion stays in motion and object at rest remains at rest. The Second law suggests that f=m*a (relation involving mass of an object and its acceleration, equals force applied). The Third law states that in every reaction, there is an equal and an opposite force. Newton’s three laws of motion are important with respect to designing bridges and elucidating the forces that cat on the bridge. Specifically, Newton’s first law of motion is crucial when the bridge is stationary, which requires the bridge to be in equilibrium, that is, the downward force exerted by the bridge is equal to the upward ground force. Regardless of different designs and complexity, all bridges have a common requirement – they should balance their live load and their dead load, failure to do that is likely to result in the bridge’s failure.

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