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UNITS AND MEASUREMENTS

Very Short Question Answers

Q1. Distinguish between accuracy and precision?

 Ans.
Accuracy Precision
1) It measures closeness of the
measured value to the true value of
quantity.		 1) This is the limit up to which a quantity can
be measured with the given instrument.
2) It depends on error 2) It does not depend on error. 

Q2. What are the different types of errors that can occur in a measurement?

Ans. i) Systematic errors: If the errors are always in one direction, then they are known as
systematic errors.
ii) Random errors: If the measured values differ from the true values irregularly both in
magnitude and sign, then these errors are known as random errors.
iii) Gross errors. 

Q3. How systematic errors be minimised or eliminated?

 Ans.
  1. By improving experimental techniques.
  2. By selecting better instruments.
  3. By removing personal bias as far as possible. 

Q4. Illustrate how the result of a measurement is to be reported indicating the error involved?

Ans. As every measurement contains errors, the result of a measurement is to be reported in
such a manner to indicate the precision of measurement.
 Measurement = A ± ∆𝐴 (∆A = error) 

Q5. What are significant figures and what do they represent when reporting the result of a measurement?

Ans. In the reported result of measurement the reliable digits plus the first uncertain digit are known as significant digits or significant figures.

They represent the precision of a measurement.

Q6. Distinguish between fundamental units and derived units?

 Ans.
Fundamental units  Derived units
  1. The units of fundamental quantities
    are called fundamental units.
  2. These are independent.
    Ex: Metre, kilogram, Second. 
  1. The units of derived quantities are
    called derived units.
  2. These are derived from fundamental
    units.
    Ex: Newton, Joule

Q7. Why do we have different units for the same physical quantity?

Ans. To measure the same physical quantity we have different units because

  1. Depends on the magnitude of the physical quantity measured.
  2. Different systems of measurements used. Ex. M.K.S System, C.G.S system, F.P.S
    system. 

Q8. What is dimensional analysis?

Ans. Dimensional analysis is a method in which fundamental quantities are raised to suitable powers to express a physical quantity.

Ex: Force:  

Q9. How many orders of magnitude greater is the radius of the atom as compared to that of the nucleus?

Ans. The radius of the atom 

The radius of the nucleus 
Hence, the radius of the atom is times greater than that of the nucleus. 

Q10. Express unified atomic mass unit in kg?

Ans.  th of the mass of carbon isotope 

Unified atomic mass unit 

Short Question Answers
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