Fundamental Quantities

Fundamental Quantities

A fundamental quantity is the quantities in which does not obtained from other physical quantity. Fundamental quantities of include

i)        Length

ii)       Mass

iii)     Time

iv)     Temperature

v)       Amount of substance (mole)

vi)     Electric current

vii)   Luminous intensity

Fundamental Quantity and Si Unity

Quantities	SI-Unit	Unit Symbol
Length	Metre	m
Mass	Kilogram	kg
Time	Second	S
Temperature	Kelvin	K
Amount of substance	Mole	mol
Electric current	Ampere	A
Luminous intensity	Candela	Cd

Three Basic Fundamental Quantities

The three basic fundamental quantities of measurement are;

i)        Length

ii)       Mass

iii)     Time 

Length 

Length is the distance between two points. Where by distance is the path taken by a particle in space between two points or object. The distance around an object is called perimeter. SI unit of length is metre (m).

It is measured by

i)        Metre rule,

ii)       Tape measure,

iii)     Vernier calliper

iv)     Micrometer screw gauge

Metre Rule

Metre rule is the mainly wooden graduated in 100 centimeters or 1metere. It is used to measure length to the nearest accuracy of 0.1cm

The reading should be perpendicular to the mark otherwise the parallax error occurs

Parallax Error

Parallax error is the apparent motion of one object related to another when the position of the eye is varied.

Vernier Calliper

Vernier calliper is an instrument used to measure length to the nearest accuracy of 0.01cm

Diagram:

i)        The inside jaws used to measure internal diameter

ii)       The external jaws used to measure external diameter

Scale of Vernier Calliper

It contains two scale namely

i)        Fixed/main scale

ii)       Vernier scale

Fixed Scale

Fixed scale gives reading in centimeter (cm) or millimeter (mm).

How to read fixed scale (M.S)

It like metre rule scale so we read as we read main scale of metre rule, the reading should take in the parallel mark between fixed scale and 0 Vernier scale mark

Vernier Scale

Vernier scale gives reading in hundredth of a centimeter (0.01cm) or thousands of millimeter (0.001mm). Vernier scale has 10 divisions which cover 9division of main scale, when this divided into 10 equal intervals the results is the difference between the main scale divisions which called least count

M.s division = 1cm/10 = 0.1cm

V.s division = 9cm/0.1 = 0.09cm

Least count = 0.1 – 0.09 = 0.01cm

How to read Vernier scale (V.S)?

The reading should take in the parallel mark between fixed scale and Vernier scale then convert it to cm or mm

Steps to Read a Vernier Calliper

i)        Read main scale (M.S)

ii)       Read Vernier scale (V.S)

iii)     Sum up the main scale (M.S) and Vernier scale (V.S)

iv)     Convert into required unit of length

Nb:

i)        Before use Vernier calipers close its jaws to determining if it contain zero error

ii)       Zero error is error arises when scale is not starting from zero mark

iii)     Zero error should be added or subtracted from all subsequent reading

Example, 

From below diagram, determine the diameter of object.

Solution:

Given

Main scale, m.s = 9.9cm

Vernier scale, v.s = 2 x 0.01 = O.02cm

Total reading (M.s + v.s) = (9.9 + 0.02) cm = 9.92cm

The diameter of object is 9.92cm

Importance of Vernier Calipers

i)        It is used to measure the internal diameter of a tube or cylinder.

ii)       It is useful in measuring the length of the object.

iii)     It is used to measure the diameter of circular objects.

 

Micrometer Screw Gauge

Micrometer screw gauge is an instrument used to measure length to the nearest accuracy of 0.001cm or 0.01mm

Diagram:

Scale of Micrometer Screw Gauge

It contains two scale namely

i)        main scale in mm

ii)       thimble scale (Circular scale)

 

Fixed Scale

Fixed scale gives reading in centimeter (cm) or millimeter (mm).

 How to read main scale (M.S)

It like metre rule scale so we read as we read mail scale of metre rule

Thimble Scale (Circular scale)

Thimble scale gives reading in thousandth of a centimeter (0.001cm). 

How to read thimble scale (T.S)?

The reading should take in the horizontal or straight line in mark or main scale

Steps to Read Micrometer Screw Gauge

i)        Read main scale (M.S)

ii)       Read Vernier scale (V.S)

iii)     Sum up the main scale (M.S) and Vernier scale (V.S)

iv)     Convert into required unit of length

 Nb:

i)        before use micrometer screw gauge close its jaws to determining if it contain zero error

ii)       zero error is error arises when scale is not starting from zero mark

iii)     Zero error should be added or subtracted from all subsequent reading 

 Example, 

From below diagram, determine the diameter of object.

Solution:

Given

Main scale, m.s = 9.5mm = 0.95cm

Thimble scale, v.s = 31 x 0.001 = O.031cm

Total reading (m.s + v.s) = (0.95 + 0.031) cm = 0.981cm

The diameter of object is 0.981cm

Note

Some distance is large and other is small to cope with this great difference, there other unity obtains from the metre, namely

Kilometre (km)

Centimetre (cm)

Millimetre (mm)

Micrometre (km)

Nanometre (nm)

Their equivalent is as follows

1km = 1000m

1m = 100cm

1cm = 10mm

1mm = 1000µm

1µm = 100nm

 

Mass

Mass is the quantity of matter in an object. SI unit of mass is kilogram (kg). It is measured by device or instrument known as beam balance. 

Beam Balance

Beam balance is the device used to measure mass of an object

Time

Time is the rate at which an event happens. It is measured by using clock or wristwatch or stopwatch

Stopwatch

Stopwatch is a device that is hold in the hand to show time elapsed