cbse class 11 physics units dimensions

1. UNIT AND MEASUREMENT
Class – 11th
Aditya Mishra
Email: adityakumar2009@gmail.com
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2. WHAT IS PHYSICS?
Physics :
• Study about nature
• Laws (rules ) of nature
Observation
• What is it ?
• Why something is happening ?
• How it is happening ?
• What if I change something ?
WHAT IS PHYSICS?
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3. WHAT IS PHYSICS?
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4. PHYSICAL QUANTITY
Physical quantity :
• Anything that can be measured is called a physical quantity
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5. TYPES OF PHYSICAL QUANTITIES
Physical Quantity
Fundamental
Physical quantity
Derived
Physical quantity
2
1
• Depends on other physical
quantity
• Many
• Independent of other physical
quantity
• only 7
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6. FUNDAMENTAL PHYSICAL QUANTITY
Fundamental physical quantity :
• A physical quantity which is independent of other physical
quantities is called fundamental physical quantity
• Only 7 in number
• Example : (1) Mass
(2) Length
(3) Time
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7. S. NO. FUNDAMENTAL
PHYSICAL QUANTITY
SYMBOL
1. Mass M
2. Length L
3. Time T
4. Thermodynamic
Temperature
θ , K
5. Strength of
Electric current
A , I
6. Amount of substance mol
7. Luminous intensity Cd
FUNDAMENTAL PHYSICAL QUANTITY
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8. DERIVED PHYSICAL QUANTITY
Derived physical quantity :
• A physical quantity which depends on other physical quantities
is called derived physical quantity
• Many in number
• Example (1) Area = Length x Width
= Length x Length
= (Length) 2
(2) Volume = Length x Width x height
= Length x Length x Length
= (Length ) 3
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9. DERIVED PHYSICAL QUANTITY
mass
(i) Density =
Volume
displacement
(ii) Velocity =
time
distance
(iii) Speed =
time
(iv) Force = mass acceleration

(v) Momentum = mass velocity

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10. UNITS
Unit :
• A fixed quantity (standard quantity) which is used to measure
an unknown quantity is called a unit
UNITS
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11. TYPES OF UNITS
• FPS (Foot, Pound, Second ) system
• CGS (Centi, Gram, Second) system
• MKS (Meter, Kilo, Second) system
• SI ( Standard International System) system
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12. C.G.S
Length
Centimeter (cm)
Time
Second (s)
Mass
Gram (g)
F. P. S
Length
foot (ft)
Time
Second (s)
Mass
Pound (lb)
M.K.S
Length
Meter (m)
Time
Second (s)
Mass
Kilogram (kg)
S.I
Length
Meter (m)
Time
Second (s)
Mass
Kilogram (kg)
TYPES OF UNITS
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13. MULTIPLES AND SUB - MULTIPLES
Multiples:
• Unit which is greater than standard unit is called multiple
• Multiple are obtained by multiplying standard unit by factors
(i) deca meter = 10 1 meter
(ii) hecto meter = 10 2 meter
(iii) kilo meter = 10 3 meter
(iv) mega meter = 10 6 meter
(v) giga meter = 10 9 meter
(vi) tera meter = 10 12 meter
deca (da) = 10 1 = 10
hecto (h) = 10 2 = 100
kilo (k) = 103 = 1000
mega (M) = 106 = 1000000
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14. Sub- Multiples :
• Units which are smaller than standard unit are called sub multiples
• Sub –multiples are obtained by multiplying with factors
MULTIPLES AND SUB - MULTIPLES
(i) deci meter = 10 1 meter
(ii) centi meter = 10 2 meter
(iii) milli meter = 10 3 meter
(iv) micro meter = 10 6 meter
(v) nano meter = 10 9 meter
(vi) pico meter = 10 12 meter
deci (d) = 10 -1 = 1/10
centi (c) = 10 -2 = 1/100
milli (m) = 10 -3 = 1/1000
micro (µ) = 10 -6 = 1/1000000
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15. DIMENSION
Dimension:
• Power to which fundamental physical quantities are raised to
obtain one unit of substance is called dimension
Example : (i) L 2 - dimension of length is 2
(ii) M 1 - dimension of mass is 1
(iii) T 3 - dimension of time is 3
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