Question
What could not be a measurement of a physical quantity?
A 10 K B 11 \(J\, N^{-1}m^{-1}\) C 17 \(Pa\, m^{3}N^{-1}\) D 25 \(T\, m\)
Answer/Explanation
Ans: B
The measurement of a physical quantity must have a value and a unit.
(A) In this option A, the value is 10 and the unit is K, hence it can represent a measurement of a physical quantity.
(B) In this option, the value is 11 and the unit is given as, J/(Nm), since Nm is also Joules, therefore the physical quantity is unit less. Hence it does not represent a measurement of a physical quantity.
(C) In this option, the value is 17 and the unit is , therefore it represents a measurement of a physical quantity.
(D) In this option, the value is 25 and the unit is Tm, hence the measurement has a value and a unit therefore it represents a physical quantity.
Hence the option (B) is correct.
Question
What is essential when recording a measurement of a physical quantity?
A the measurement has an SI unit
B the measurement has a unit and a number
C the measurement has a unit given as a base unit
D the measurement is from an analogue scale
Answer/Explanation
Ans :B
The measurement should have a value as a number and a unit.
(A) The measurement must also have a number and not just unit, hence the option is not correct.
(B) The measurement has a unit and a number therefore it can represent a physical quantity and the option is correct.
(C) If the measurement has only unit it can not be a measurement of a physical quantity, hence the option is incorrect.
(D) The measurement must also have a unit, therefore the option is incorrect.
Question
What is a reasonable estimate of the volume of an adult person?
A 0.10 m³ B 0.50 m³ C 1.0 m³ D 2.0 m³
Answer/Explanation
Ans: A
The average height of a person is 1.8 m, the width is 0.6 m and the thickness is 0.1 m, therefore the volume will be given as ,
Question
The table shows some measurable quantities. Which row gives the correct order of magnitude of the measurable quantity in the stated unit?
(A) The mass of a coin is approximately 5 grams hence it is much greater than , hence the option is incorrect.
(B) The thickness of a paper is in millimeter hence it is less than m therefore the option is incorrect.
(C) The mass of an apple is approximately 125 grams therefore the weight of the apple is
Hence the option (C) is correct.
Answer/Explanation
Ans:C
Question
Which quantity is a physical quantity?
A atomic number
B efficiency
C number density of charge carriers
D strain
Answer/Explanation
Ans: C
(A) The atomic number is not a physical quantity because it does not have a unit. Atomic number is a chemical property. Hence the option is incorrect.
(B) The efficiency does not have a unit, hence it is not a physical quantity.
(C) The number density has a unit of therefore it is a physical quantity.