Write a short summary of these chapters in 200 words :
Measurements and •Experimentation
•Motion in one Dimension
•Laws of Motion
•Pressure in Fluids and •Atmospheric Pressure
•Upthrust in Fluids , Archimedes Principle and Floatation
•Heat and energy
•Reflection of Light
•Current Electricity
•Magnetism
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Answers
Answer:
Measurement: Measurement is the process of comparison of the given physical quantity with the known standard quantity of the same nature.
Unit: Unit is the quantity of a constant magnitude which is used to measure the magnitudes of other quantities of the same nature.
Metre: A metre is defined as the distance between two marks drawn on the platinum-iridium rod kept at 0oC in the International Bureau of Weights and Measures at Sevres near Paris.
Kilogramme: A kilogramme is defined as the mass of a cylindrical piece of platinum-iridium alloy kept in International Bureau of Weights and Measures at Sevres near Paris.
Second: A second is defined as 1/86400 the part of a mean solar day.
Estimation by Orders of Magnitude
The order of magnitude of a physical quantity is its magnitude in powers of ten when that physical quantity is expressed in powers of ten with one digit to the left of the decimal.
If the thickness of a card sheet is 0.0027 m = 2.7 x 10-3 m
Then its order of magnitude will be 10-3 m
General Formula: Physical quantity = M x 10n
10 < M < 1.
“n” is a positive or negative integer.
The power of ten (i.e. 10n) is called the order of magnitude of the physical quantity.
M is called its numerical value.
While expressing the order of magnitude of a physical quantity, its unit must be mentioned because, by the change of unit, the power of ten in its magnitude will also change: The order of 2.7 x 10-3 m ≠ the order of 2.7 x 10-1 cm.
Measurement
The result of measurement can be expressed in terms of the following two terms:
The unit in which the quantity is to be measured.
The numerical value which expresses, how many times the unit is contained in the given quantity.
Thus, Physical quantity = (numerical value) x (unit)
Choice of Unit (SARC)
The unit should have the following properties:
The unit should be of convenient size.
It should be possible to define the unit without ambiguity.
The unit should be reproducible.
The value of unit should not change with space and time.
The last three conditions are necessary for the unit to be accepted internationally.
Fundamental or Basic Units
A fundamental or basic unit is that which is independent of any other unit or which can neither be changed nor can be related to any other unit.
The units of mass, length, time, temperature, current and amount of substance are fundamental units.
Derived Units
Derived units are those which depend on the fundamental units or which can be expressed in terms of the fundamental units.
For example, for the measurement of area, we need a unit which is length x length or (length)2
Sub units of metre:
1 centimetre (cm) = 10-2 m.
1 millimetre (mm) = 10-3 m.
1 micron (m) = 10-6 m.
1 nanometer (nm) = 10-9 m.
Multiple units of metre:
1 kilometre (km) = 103 m.
Non-metric units of metre:
1 Astronomical unit (A.U.) = 1.496 x 1011 m.
1 Light year (ly) = 9.46 x 1012 m.
1 Parsec = 3.08 x 1016 m.
Smaller units of metre:
1 Angstrom (Å) = 10– 10 m.
1 fermi (f) = 10-15 m.
Units of mass (S.I. unit is kg).
Sub units of kilogramme
1 gramme (g) = 10-3 kg.
1 milligramme (mg) = 10-6 kg.
Multiple units of kilogramme
1 quintal = 102 kg.
1 metric tonne = 103 kg.
Non-metric units of kilogramme
1 atomic mass unit (a.m.u.) = 1.66 x 10-27 kg.
Larger units of kilogramme
1 solar mass = 2 x1030 kg.
Units of time (S.I. unit is s).
Common units of time
1 Minute (min) = 60 s.
1 Hour (h) = 3600 s.
1 Day = 86400 s.
1 Month is approx. equal to 30 days.
1 Lunar month is nearly equal to 27.3 days.
1 year (yr) = 365 days.
1 Leap year = 366 days.
1 decade = 10 years.
1 century = 100 years.
1 millennnium = 1000 years.
Guidelines for Writing Units
The symbol for a unit, which is not named after a scientist, is written in the lower letter. For example g, kg, s.
The symbol for a unit, which is named after a scientist, is written with the first letter of his name in capital. For example Pa for pascal, J for joule.
The full name of the unit, even when it is named after a scientist, is written with a lower initial letter. For example unit of force is written as newton and not as Newton.
A compound unity formed by multiplication of two or more units is written after putting dot, cross or leaving a space in between the two symbols. For example, the unit of torque is written as N.m or Nm or N m.
Negative power is used for compound units, which are formed by dividing one unit by the other. The unit of velocity is (metre \ second ) and is expressed as ms–1