The subject of Motion has been of great interest for scientists in the past and present. If we define Motion in simple terms, it is nothing but the change in the location of a body, and any change in Motion can result from the application of an external force. In the subject of physics, motion is described in terms of velocity, acceleration, displacement, and time (Nave). This paper briefly describes the development of scientific knowledge and the ideas of Motion that came through the ages.
According to the historical evidence it is said that Aristotle (350 BC) was the first person to study Motion, and he imagined heavier objects fell faster. In other words, he linked Motion to the weight of the object. Aristotle also linked any kind of change to Motion. In his studies, he defines Motion as the actuality of a potentiality. He uses the words energeia (which means being-at-work) and entelechy (which means being-at-an-end) to describe a kind of action (Sachs).
Galileo Galilei (1589) is said to be the first person to investigate Motion. He was an Italian natural philosopher, astronomer, and mathematician. His contributions to the sciences of Motion, astronomy, and the development of the scientific method were considered great. His formulation of (circular) inertia, the law of falling bodies, and parabolic trajectories marked the beginning of a fundamental change in the study of Motion (Encyclopedia Britannica). Galileo spent his final years basically to write on the laws of force and Motion. In the book ‘Dialogues on the Two New Sciences, published in 1638, his work on Motion, acceleration, and gravity is lucidly explained. This became a basis for the three laws of Motion by Sir Isaac Newton in 1687 (The Robinson Library).
The work of Robert Hooke (1657) on Motion was also considered to be of great significance. He showed that a feather and a coin fall at the same rate in a vacuum. In his ‘Attempt to Prove the Motion of the Earth’ (1674), he presented a theory of planetary Motion based on the proper principle of inertia and a balance between an outward centrifugal force and an inward gravitational attraction to the Sun (roberthooke.org.uk).
Sir Isaac Newton was the greatest contributor to the ideas of Motion. He published his three laws of MotionMotion and his law of gravitation in 1687. Newton’s laws of Motion are three laws which present relationships between the forces acting on a body and the Motion of the body.
- The First Law of Motion states that “A particle will stay at rest or continue at a constant velocity unless acted upon by an external unbalanced net force.” Newton explains that it is possible to select a set of reference frames, called inertial reference frames, observed from which a particle moves without any change in velocity if no net force acts on it (Fig. 1).
- The second law states that “F = ma. The net force on an object is equal to the mass of the object multiplied by its acceleration.” The net force on a particle is proportional to the time rate of change of its linear momentum when observed from the inertial reference frame. This is expressed as F = d (mv) / dt. Momentum is the product of mass and velocity. Force and momentum are vector quantities (i.e., they have a specific direction), and the resultant force is found from all the forces present by vector addition.
- The third law states that “Every action has an equal and opposite reaction.” In other words, whenever a particle exerts a force on another particle, the other particle also simultaneously exerts a force on the first particle with the same magnitude and in the opposite direction (Warren).
Albert Einstein contributed his theory of relativity (1905) and showed that Newton’s Law are not completely true when it comes to the very fast velocities. Einstein recognised that the speed of light in a vacuum is constant and an absolute physical boundary for Motion. For objects travelling at or near the light speed, the theory of relativity states that objects will move slower and shorten in length from the point of view of an observer on Earth. Einstein also derived the famous equation, E = mc2, which reveals the correspondence of mass and energy (AllAboutScience.org).
Work Cited
Theory of Relativity – The Basics [2008]. Web.
Encyclopedia Britannica. Galileo Galilei [2008]. Web.
Nave, R. Motion. HyperPhysics. (2005).
Georgia State University [2008]. Web.
roberthooke.org.uk. Robert Hooke [2008]. Web.
Sachs J. Aristotle (384-322 BCE): Motion and its Place in Nature (2006) The Internet Encyclopedia of Philosophy. Web.
The Robinson Library. Galileo Galilei [2008]. Web.
Warren N. G. Excel Preliminary Physics. Glebe NSW: (2000). Pascal Press, ISBN 1740200853.
