Selina ICSE Solutions for Class 9 Physics Chapter - 1 Measurements and Experimentation Exercise 1(A) 1. What is meant by measurement? Solution 1. Measurement is the process of comparing a given physical quantity with a known standard quantity of the same nature. 2. What do you understand by the term unit? Solution 2. Unit is a quantity of constant magnitude which is used to measure the magnitudes of other quantities of the same manner. 3. What are the three requirements for selecting a unit of a physical quantity? Solution 3. The three requirements for selecting a unit of a physical quantity are 1. It should be possible to define the unit without ambiguity. 2. The unit should be reproducible. 3. The value of units should not change with space and time. 4. Define the three fundamental quantities. Solution 4. Definitions of three fundamental quantities: 1. S.I. unit of length (m): A metre was originally defi...
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