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?
▶️Answer/Explanation
(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
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.