Units And Measurements

Question 1

Physical quantity

Answer 1

Any quantity that can be measured directly or indirectly

Question 2

Fundamental Quantities

Answer 2

Quantities which cannot be expressed in terms of simpler quantities and are independent of other physical quantities

Question 3

7 fundamental quantities

Answer 3

Length
Mass
Time
Temperature
Electric Current
Luminous Intensity
Amount of Substance

Question 4

Derived quantities

Answer 4

Quantities which are derived from different combinations of fundamental quantities

Question 5

Units of fundamental quantities

Answer 5

Fundamental Units

Question 6

Units of derived quantities

Answer 6

Derived units

Question 7

System of units

Answer 7

A system of units is a complete set of units that are needed to measure all fundamental and derived quantities

Question 8

Examples of systems of units (4)

Answer 8

CGS
MKS
FPS
SI

Question 9

SI unit

Answer 9

SI units are a common system of units that are internationally accepted. It is based on seven fundamental units and two supplementary units

Question 10

SI unit is based on?

Answer 10

Seven fundamental units and two supplementary units

Question 11

SI unit of Mass

Answer 11

kg

Question 12

SI unit of length

Answer 12

m

Question 13

SI unit of Time

Answer 13

s

Question 14

SI unit of Electric Current

Answer 14

A

Question 15

SI unit of Temperature

Answer 15

K (Kelvin)

Question 16

SI unit of Amount of Substance

Answer 16

mol (moles)

Question 17

SI unit of Luminous Intensity

Answer 17

cd (candella)

Question 18

Plane Angle

Answer 18

Radian

Question 19

Solid Angle

Answer 19

Steradian

Question 20

Advantages of SI system (3)

Answer 20

Rational
Metric
Coherent

Question 21

SI units are rational?

Answer 21

Each quantity only has one unit

Question 22

SI units are metric?

Answer 22

The multiples and sub-multiples of SI units are in powers of 10

Question 23

SI units are coherent?

Answer 23

Simple multiplication and division of fundamental units can be used to obtain all derived units without any numerical factor

Question 24

Dimensions

Answer 24

Dimensions are the powers to which fundamental quantities are to be raised to represent any given physical quantity

Question 25

Dimensional Constants

Answer 25

g, G

Question 26

Dimensionless Constants

Answer 26

π, 1/2, 2...

Question 27

Dimensional Variable

Answer 27

Pressure, Work..

Question 28

Dimensionless Variables

Answer 28

Plane Angle, refractive index...

Question 29

1st application of dimensional analysis

Answer 29

To check dimensional correctness or consistency of equations

Question 30

2nd application of dimensional analysis

Answer 30

To derive relationships among different physical quantities

Question 31

Dimensional correctness aka?

Answer 31

Dimensional consistency

Question 32

Principle of homogeneity

Answer 32

The principle of homogeneity states that a physical equation will only be correct if the dimensions of all the terms on either side are the same. Only terms that have the same dimensions can be added or subtracted.

Question 33

1st limit of dimensional analysis

Answer 33

Dimensional analysis does not give any information about the proportionality constant

Question 34

2nd limit of dimensional analysis

Answer 34

It fails when a physical quantity depends on more than three other quantities

Question 35

3rd limit of dimensionless analysis

Answer 35

It fails when a physical quantity is a sum or difference of other quantities.

Question 36

4th limit of dimensional analysis

Answer 36

It fails to derive relationships which involve dimensionless quantities like trigonometric functions

Question 37

Limitations of dimensional analysis (4)

Answer 37

Proportionality constant Dependent on more than three other quantities Sum or difference of other quantities Dimensionless like trig

Question 38

Significant digits

Answer 38

Significant digits are those digits in a measurement which are known to be reliable and the first unreliable digit

Question 39

Accuracy

Answer 39

Accuracy is the closeness of the measured value to the true value of the quantity

Question 40

Precision

Answer 40

Precision is the resolution to which a quantity can be measured