27-06-2014, 11:54 AM
PHYSICS
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Nature of the
Physical World and Measurement
The history of humans reveals that they have been making
continuous and serious attempts to understand the world around them.
The repetition of day and night, cycle of seasons, volcanoes, rainbows,
eclipses and the starry night sky have always been a source of wonder
and subject of thought. The inquiring mind of humans always tried to
understand the natural phenomena by observing the environment
carefully. This pursuit of understanding nature led us to today’s modern
science and technology.
1.1 Physics
The word science comes from a Latin word “scientia” which means
‘to know’. Science is nothing but the knowledge gained through the
systematic observations and experiments. Scientific methods include
the systematic observations, reasoning, modelling and theoretical
prediction. Science has many disciplines, physics being one of them.
The word physics has its origin in a Greek word meaning ‘nature’.
Physics is the most basic science, which deals with the study of nature
and natural phenomena. Understanding science begins with
understanding physics. With every passing day, physics has brought to
us deeper levels of understanding of nature.
Physics is an empirical study. Everything we know about physical
world and about the principles that govern its behaviour has been
learned through observations of the phenomena of nature. The ultimate
test of any physical theory is its agreement with observations and
measurements of physical phenomena. Thus physics is inherently a
science of measurement.
Physics, Technology and Society
Technology is the application of the doctrines in physics for
practical purposes. The invention of steam engine had a great impact
on human civilization. Till 1933, Rutherford did not believe that energy
could be tapped from atoms. But in 1938, Hann and Meitner discovered
neutron-induced fission reaction of uranium. This is the basis of nuclear
weapons and nuclear reactors. The contribution of physics in the
development of alternative resources of energy is significant. We are
consuming the fossil fuels at such a very fast rate that there is an
urgent need to discover new sources of energy which are cheap.
Production of electricity from solar energy and geothermal energy is a
reality now, but we have a long way to go. Another example of physics
giving rise to technology is the integrated chip, popularly called as IC.
The development of newer ICs and faster processors made the computer
industry to grow leaps and bounds in the last two decades. Computers
have become affordable now due to improved production techniques
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and low production costs.
The legitimate purpose of technology is to serve poeple. Our society
is becoming more and more science-oriented. We can become better
members of society if we develop an understanding of the basic laws of
physics.
Newton’s law of gravitation
The motion of the planets, the moon and the Sun was the interesting
subject among the students of Trinity college at Cambridge in England.
Isaac Newton was also one among these
students. In 1665, the college was closed for an
indefinite period due to plague. Newton, who
was then 23 years old, went home to
Lincolnshire. He continued to think about the
motion of planets and the moon. One day
Newton sat under an apple tree and had tea
with his friends. He saw an apple falling to
ground. This incident made him to think about
falling bodies. He concluded that the same force
of gravitation which attracts the apple to the
Earth might also be responsible for attracting
the moon and keeping it in its orbit. The centripetal acceleration of the
moon in its orbit and the downward acceleration of a body falling on the
Earth might have the same origin. Newton calculated the centripetal
acceleration by assuming moon’s orbit (Fig. 4.1) to be circular.