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Physics Part I

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CBSE Gujarat Board Haryana Board

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Class 10 Class 12
The shells of crabs found around a particular coastal location in Japan seem mostly to resemble the legendary face of a Samurai. Given below are two explanations of this observed fact. Which of these strikes you as a scientific explanation ?
(a) A tragic sea accident several centuries ago drowned a young Samurai. As a tribute
to his bravery, nature through its inscrutable ways immortalised his face by imprinting it on the crab shells in that area.
(b) After the sea tragedy, fishermen in that area, in a gesture of honour to their dead hero, let free any crab shell caught by them which accidentally had a shape resembling the face of a Samurai. Consequently, the particular shape of the crab shell survived longer and therefore in course of time the shape was genetically
propagated. This is an example of evolution by artificial selection.
[Note : This interesting illustration taken from Carl Sagan’s ‘The Cosmos’ highlights
the fact that often strange and inexplicable facts which on the first sight appear  ‘supernatural’ actually turn out to have simple scientific explanations. Try to think
out other examples of this kind].

Explanation (b) is the correct scientific explanation of the given fact. 


Name some of the popular branches of science.

Some of the popular branches of science are:
  1. Physics
  2. Chemistry
  3. Botany
  4. Zoology
  5. Geology

What do you understand by matter? What are its different phases? 

Any thing that possesses weight and occupies space is called matter.

The three phases of matter are: 

  1. Solid state
  2. Liquid state
  3. Gaseous state

In Physics, matter and energy are used together in an equation. What is the relation between them?

Yes, the mass of an object is a measure of its energy content. 

The relation between mass-energy is given by, 
                              E =mc2

m = Mass of an object
c  = Speed of Light

This equation is also known as Mass-Energy Equivalence relation. 

What is Physics?

Physics is that branch of science which deals with the study of properties of matter, energy and their interactions.


What is science?

The word Science originates from the Latin verb Scientia meaning 'to know'. 

Science is a systematic attempt to understand natural phenomena in as much detail and depth as possible, and use the knowledge so gained to predict, modify and control phenomena. Science is exploring, experimenting and predicting from what we see around us.