There are four fundamental forces which govern both macroscopic and microscopic
phenomena. These are
(i) Gravitational force
(iii) Electromagnetic force
(ii) Nuclear force
(iv) Weak force
All those quantities which can be measured directly or indirectly and in terms of which
the laws of physics can be expressed are called physical quantities
The units of the fundamental quantities called fundamental units , and the units of
derived quantities called derived units.
DIMENSION & DIMENSIONAL FORMULA:
The equation which expresses a physical quantity in terms of the fundamental
units of mass, length and time, is called dimensional equation.
According to the principle of homogeneity a physical equation will be
dimensionally correct if the dimensions of all the terms in the all the terms
occurring on both sides of the equation are the same.
There are three main uses of the dimensional analysis-
1.To check the correctness of a given physical relation.
2.To derive a relationship between different physical quantities.
Significant figures: - The significant figures are normally those digits in a
measured quantity which are known reliably plus one additional digit that is
uncertain.
RULES OR FINDING SIGNIFICANT FIG.:
(i) All non- zero digits are significant figure.
(ii) All zero between two non-zero digits are significant figure.
(iii) All zeros to the right of a non-zero digit but to the left of an understood decimal
point are not significant. But such zeros are significant if they come from a
measurement.
(iv) All zeros to the right of a non-zero digit but to the left of a decimal point are
significant.
(v) All zeros to the right of a decimal point are significant.
(vi) All zeros to the right of a decimal point but to the left of a non-zero digit are not
significant. Single zero conventionally placed to the left of the decimal point is
not significant.
(vii) The number of significant figures does not depend on the system of units.
phenomena. These are
(i) Gravitational force
(iii) Electromagnetic force
(ii) Nuclear force
(iv) Weak force
All those quantities which can be measured directly or indirectly and in terms of which
the laws of physics can be expressed are called physical quantities
The units of the fundamental quantities called fundamental units , and the units of
derived quantities called derived units.
DIMENSION & DIMENSIONAL FORMULA:
The equation which expresses a physical quantity in terms of the fundamental
units of mass, length and time, is called dimensional equation.
According to the principle of homogeneity a physical equation will be
dimensionally correct if the dimensions of all the terms in the all the terms
occurring on both sides of the equation are the same.
There are three main uses of the dimensional analysis-
1.To check the correctness of a given physical relation.
2.To derive a relationship between different physical quantities.
Significant figures: - The significant figures are normally those digits in a
measured quantity which are known reliably plus one additional digit that is
uncertain.
RULES OR FINDING SIGNIFICANT FIG.:
(i) All non- zero digits are significant figure.
(ii) All zero between two non-zero digits are significant figure.
(iii) All zeros to the right of a non-zero digit but to the left of an understood decimal
point are not significant. But such zeros are significant if they come from a
measurement.
(iv) All zeros to the right of a non-zero digit but to the left of a decimal point are
significant.
(v) All zeros to the right of a decimal point are significant.
(vi) All zeros to the right of a decimal point but to the left of a non-zero digit are not
significant. Single zero conventionally placed to the left of the decimal point is
not significant.
(vii) The number of significant figures does not depend on the system of units.
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