class 7

1. Measurement

2. Measurement
 Measurement: Measurement is the comparison of
unknown physical quantity with a known standard
quantity of same kind.
 Physical quantity: Those quantity which can be
measure are called physical quantity. For
examples:length,mass,time,temperature,electric
current, luminous intensity and amount of substance
etc.
 Standard quantity: Known quantity

3. SI system
 SI system: The 12th General Conference of weight and
Measurement held in France in October 1960 made an
agreement to use international system of unit to bring
uniformity in he measurement. It is an internationally
accepted system and have the same value all over the
world.SI system is also known as SI unit.
 In this system length is measured in metre,mass in
kilogram and time in second.
 SI unit are divided into two group: They are
fundamental and derived units.

4. Systems of unit
 CGS system:CGS system is the system of measurement in
which length is measured in centimetre,mass is measured
in gram and time is measured in second. It is also known as
French system of measurement.
 FPS system:FPS system is a system of measurement in
which length is measured in foot, mass is measured in
pound and the time is measured in second. It is also
known as British system of measurement .
 MKS system:MKS system is the system of measurement in
which length is measured in metre,mass is measured in
kilogram and time is measured in second. It is also known
as Metric system of measurement .

5. Fundamental units
 The units that are independent of other units are
called fundamental units.
Forexamples:length,mass,time,temperature,electric
current, luminous intensity and amount of substance
etc.

6. Derived units
 The units which are derived from the fundamental
units are called derived unit. For examples:

7. Length and its measurement
 Length refers to the distance between two
points.Height,breadth,thickness,diameter,radius etc
are also the forms of the
length.Scale,metre,rod,measuring tape etc.
 Unit of length:

9. Mass and its measurement
 The total amount of matter contained in a body is
called mass .Its SI unit is Kilogram (kg).It can also be
measured in gram,milligram,quintal or metric ton
according to the size or amount of the mass . We use
beam balance to measure the mass of an object.

11. Time and its measurement
 The duration or interval between two successive event
is known as time. Its SI unit is second(s).Instrument
use to measure the time are pendulum clock, electric
clock digital clock etc.

12. Regular and Irregular objects
 Regular object: The objects which have a fixed
geometrical shape and proper dimension are known as
regular objects. For examples book ,pen chalk, brick
etc
 Irregular objects: The objects which do not have a
definite geometrical shape and proper dimension are
known as irregular objects. For examples stone, leaf,
broken glass etc.

13.  Area=The region occupied by the plane surface of
object is called area. Its SI unit is square meter( m2 )
 Measurement of area of regular objects=We can
measure the area of regular objects by using their
respective formula.
1. Area of a rectangle: Area=length(l) x breadth(b)
2. Area of square: A=l x l
 Measurement of area of irregular objects=We
can measure the area of irregular object by using
graph paper.

14. Volume
 The total space occupied by an object is called its
volume. Its SI unit is cubic meter(m3) 1000cm3 =1liter
 We can measure the volume of liquid by keeping it in
a measuring vessel such as measuring cylinder, conical
flask,pipette,burette.
 We can measure the volume of irregular solid objects
by using a measuring cylinder applying water
displacement method.