Class 9th // Physics // Short Answer Type Questions ## Chapter - Science and Measurement
» very short answer type questions
Question 1. What is science?
Answer :- The knowledge gained through careful and systematic experiments and tests is called science.
Question 2. How many types of physical quantities are there? Write their names.
Answer :- There are two types of physical quantities.
(i) Base quantities
(ii) Derived quantities
Question 3. What is base quantities?
Answer :- All those quantities which are considered independent are called base quantities.
Eg:- length, time, mass
Question 4. What is Derived quantities?
Answer :- All those quantities which are expressed in terms of basic quantities signs are called Derived quantities.
Eg:- Area, Volume, force, Work, Energy
Question 5. What is the basic unit?
Answer :- Such a unit which does not depend on any other unit, that is, such a unit from which all other units are obtained, is called basic unit.
Question 6. What is meant by system of units?
Answer :- Units are used to measure physical quantities, such as meter, centimeter or foot are used to measure distance and kg, g etc. are used to measure mass, this made The method is called the method of units.
Question 7. What are the units of radian and steradian?
Answer: Radian is the unit of plane angle and steradian is unit of solid angle.
Question 8. One nanometer (nm) is equal to how many metres?
Answer :- 10‐⁹ is equal to fraction.
Question 9. What is light year?
Answer :- The total distance covered by light in one year is called a light year.
» Short Answer Type Questions
Question 1. What things are necessary to know for a complete description of the magnitude of a quantity? Share with an example.
Answer :- The magnitude of a quantity is determined by comparing it with its unit.
For example, when we say that the length of a table is 2 meters, it means that if two meter scales are placed end to end in a proof, they will be equal to the length of the table.
Question 2. What are the base quantities and the derived quantities? Give two examples of these.
Answer :- Base quantities - All those quantities which are considered independent, they are called base quantities .
Eg:- length, time, mass
Derived quantities - All those quantities signs which are expressed in terms of basic quantities signs are called Derived quantities .
Eg:- Area, Volume, force, Work, Energy
» Long Answer Questions
Question 1. Mention any three things to be kept in mind while writing the abbreviations of SI units with examples.
Answer :- (I) English names of units should not start with capital letter.
Eg :- Writing 1 Ampere is wrong.
It is correct to write 1 ampere.
(II) Plural is not used in units.
Eg :- Not grams, gram is written.
(III) In Hindi also, the abbreviations of the units should be written in English letters only.
Like :- Kilogram to kg.
