Introduction to Newton’s First Law
Newton’s First Law of Motion has two situations: first describes the reason for a state of any object and second defines inertia. It is a profound law given by Newton in the 17th century that rules all classical mechanics. A new era of science was evolved by the development of this law. Newton imagines the position of an object as its reaction towards the external parameter. in a straight line and says that a body’s position is fixed at its point until some external parameter disturbs it. Similarly, he says that a moving object continues its motion with uniform speed in that straight line again until the parameter disturbs the motion. This external parameter was later assigned as force. Again, he clarifies that the force causing the change is an imbalanced force. A balanced force has net effect zero and the object continues to its state.
Before the theory, a lot of rumors on the behavior of motion were scattered in certain papers. He put all the theories under the same roof and clarified the concept of rest, motion, gravity and all small parameters associated with gravity. Rest and motion almost include every activity of any object. Thus the physics about them was very necessary at the time to understand their behavior and predict their position after a moment. The term force was first discovered by Newton. Physics today may have taken another direction but is always rooted to Newtonian mechanics.
Understanding the Principle of Inertia
Newton defined inertia and showed it as that property which keeps the object continuing its position until any disturbance comes to it. We can physically experience inertia while suddenly changing our position. When force and inertia meet head to head, the state of the object changes. But, inertia leaves with a print. Simple example demonstrating inertia is what we feel when we come to rest suddenly while moving on a vehicle. We feel a shocking pull towards the front because of the inertia of motion.
Inertia is in the opposite nature with force. The force bringing a change must be larger than this inertia to show its strength.
Inertia is a simple concept to define but to see its role in physics; a different system can be brought. These physical systems are taken as different inertial frames. An object at one frame of reference takes it as a standpoint to view the motion of another object in another frame of reference. Two objects, one at rest and other at motion have different physics of another object lying in the other frame. Similarly, a non-moving frame and a moving frame can have different forces, velocities, impact of gravity and many other physical parameters. Taking these inertial frames to a celestial view, we get a broader thinking of inertia, forces and motions.
Historical Context: From Aristotle to Newton
Before Newton, Aristotle’s theory about motion lasted for centuries. Aristotle believed that a certain factor (force) was responsible for carrying on the motion of an object which would naturally come to rest. He called the falling motion as natural motion which solely depended on its composition. For example, the nature of air and fire was to move upward and they would seek their own direction. Heavy materials like humans were earth’s composition and they would naturally come to earth. Aristotle’s motion was highly pointed towards vertical motion. According to him, horizontal motion was generated due to some push or a pull. He named such motions as violent motion. He described projectile motion as the combination of both natural and violent motion. According to Aristotle’s theory, an object thrown was first dragged by a force then it would gradually keep forgetting the force and finally come to rest naturally.
Aristotle’s concept was totally discarded by Galileo and argued that an object cannot be at rest or in motion naturally. There was an external feature to drag them. He also stated that in the absence of friction and other external forces, objects tend to continue moving consistently. Aristotle’s theory requires force to continue in horizontal motion while Galileo objects it and says that force is not necessary to keep an object in motion. Force is a factor to bring it to rest.
Galileo’s experiments with inclined planes provided heavy support to his hypothesis. The inclined plane experiment was done with a ball of certain mass which fell uniformly throughout the plane. Same experiment was used to describe projectile motion. The nature of motion was pictured graphically (parabolic path) with the help of time and distance calculation. He was also able to determine the falling rate. His theory correctly proves that the motion of the projectile was uniform and could continue in the same way in the absence of force.
Newton used Galileo’s theory as a reference to develop his law of universal gravitation and other three main laws of motion. Galileo’s idea and Newton’s first law both agree on the nature of motion and the nature of gravity that pulls anything towards it.
Mathematical Expression of the First Law
Newton’s law is more like a conceptual law. To show it mathematically, let us consider ‘n’ different kinds of forces in action then the net sum of these forces is zero.
In vector representation, let F1, F2, F3…, Fn be the total forces available. Then their vector sum is represented as:
Fnet = F1+F2+F3,…,+Fn
=> Fnet = n∑1Fi [Equation 1]
To validate the first law, equation [1] must be zero i.e.
n∑1→Fi = 0 [Equation 2]
Thus we can conclude that an object will either stay at rest (if initially at rest) or continue moving in a straight line at constant speed (if initially in motion).
Real-World Examples Illustrating Newton’s First Law
- A glass placed on a plane table: Any object placed over a plane surface on earth remains in its state. For example, a glass placed on a table doesn’t move itself until a force acts on it. This is in accordance with the first law.
- A marathoner: A participant in a marathon, after reaching the end point still goes running forward for a while due to inertia of motion.
- A passenger inside a car: When a person is set to go in a car, he feels a backward push after sudden start of the car. This resembles the inertia of rest not prepared for motion.
- Shaking tree: A tree is always in rest position but on shaking its parts, the inertia of rest gets disturbed. Leaves are not ready for the motion, while the sudden movement of the branches exhibit the falling of leaves or fruits from the tree.
- A balloon: When a balloon is blown and released, it tries to keep floating upward. However, certain entities like air resistance, gravity, friction etc. makes the balloon come to rest.
- A rolling ball: According to Newton’s first law, if no forces act on a ball rolling on the ground, it will continue to roll indefinitely. Still the force of friction applied by ground helps the ball to bring it to rest.
Applications in Modern Engineering and Technology
Newton’s First Law is highly applied in today’s engineering systems and techniques. Implying inertia in automobile design helps engineers in building good safety measures like seatbelts and airbags, which lessen the injury from sudden incidents and collisions. Some important applications are given below:
- Automobile safety: Knowing the results of inertia of rest and motion, seat belts and airbags are designed in automobiles to prevent sudden hits and injuries.
- Railways and metros: Magnetic braking systems are developed in trains to get a predictable stop and reduce the possible halts.
- Smartphone sensors: Engineers are able to study the previous or initial position of the object and sensor the changes like biometrics, fitness tracking, lighting etc.
- Structural design: Earthquake causes sudden motion on the buildings and structure at rest which causes a serious destruction. So, to overcome this, engineers design the base with dampers and isolators which absorb the motion and reduce the effect of inertia.
- Aerospace and Aviations: In autopilot systems, Gyroscope maintains the navigation, studying the orientation of the design based on inertial activities.
- Satellite orbiting: A satellite keeps on moving in its trajectory unless acted by a force according to the law. Hence, engineers use this principle to keep track of the satellite and control its motion.
Common Misconceptions About Inertia and Motion
Newton’s law is very simple but sometimes it is misunderstood with Aristotle’s theory. Confusion also arises between the terms inertia and force. Some of the confusions and clarifications are given below:
- Inertia is thought to be a force: Inertia lets an object to be in the state of rest or motion and resists force. Inertia and force are strongly opposite entities. Therefore we can call it as a property to withstand a state but is certainly not a force
- Force and motion: People often think that a force is responsible to continue the motion of an object. However, force brings the change in the state of motion but is not responsible to carry on the movement. An object can continue its motion to infinity if force is absent or balanced. Force is only required to boost the speed or bring the object to rest.
- Heavier Objects Fall Faster Than Lighter Ones: This is the Aristotalian theory which was already rejected by Galileo’s mathematical and experimental analysis. The mass matters only if the air is present and it doesn’t affect the inertia of motion or rest.
- An Object at Rest Has No Forces Acting on It: An object at rest is of course not acted by any force. The net force here may be the result of resultant force which is zero. This is called a balanced force.
- Moving object slows down due to inertia: Inertia never wants a change so the slowing motion may be the result of external forces or friction.
Experimental Demonstrations of the First Law
Newton’s first law can be easily shown in a classroom. Some of the techniques are given below:
- Put a glass above a handkerchief on a plane surface. Pull the handkerchief suddenly. You can see the glass standing as it is showing inertia of rest.
- Pull a book quickly from a stacked place in a book shelf. The book comes out keeping the book on top in its place.
- Kicking a ball: A ball at rest comes to motion while kicking and rolls continuously. It tries to be in motion unless a force or friction acts on it.
- Keep a coin on paper. Snatch the paper suddenly and you see the coin staying still in its position.
These demonstrations help to visualize the law in action and understand the concept of inertia.
The First Law’s Role in the Broader Framework of Classical Mechanics
Newton’s first law was derived later after the evolution of Newton’s universal law of gravitation. Later, other two laws successfully emerged making Newton’s idea more powerful. Definition of rest and motion was provided by the law which governed everything from minute to major scales of the universe. A universal property known as inertia was brought into the spotlight which changed the concept about rest and motion. This law also provided the standard of reference to measure motion and force.
By the generalization of Newton’s first law a major branch of physics evolved known as classical mechanics. Other major branches like cosmology, General theory of relativity and also quantum mechanics rely on Newtonian mechanics.
Conclusion
Newton’s First Law of Motion created a drastic change in the understanding of motion and force. By proving that objects keep their state unless acted upon by a net external force, Newton established a new paradigm breaking all the stereotypes that force is required to continue in motion.
This principle revealed the concept of inertia which is a foundation for physicists and engineers. It has been employed from designing safer vehicles to navigating spacecraft. First Law is always inspiring advancements in machineries to our knowledge of rest and motion. We cannot stop appreciating the conceptual depth of the First Law and its real-world relevance. By continuously studying and advancing classical mechanics, we are providing an honor to Newton’s legacy for his fundamental workings on the universe.
References
Halliday, D., Resnick, R., & Walker, J. (2013). Fundamentals of physics (10th ed.). Wiley.
Galili, I., & Tseitlin, M. (2003). Newton’s First Law: Text, translations, interpretations and physics education. Science & Education, 12(1), 45-73.
Newton’s First Law
https://www.geeksforgeeks.org/physics/newtons-first-law-of-motion/
https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/newtons-laws-of-motion/
