physics

Physical quantities may be variable and constants. They may have dimension or could be dimensionless.

i)                DIMENSIONAL VARIABLE: These are the quantities which are variable and have dimensions as well. example Velocity, acceleration, force, etc.

ii)             Dimensional constant: These are the quantities which have constant values and yet have dimensional example. Gravitational constant, coefficient of viscosity, Planck’s constant, velocity of light etc. Their numerical value does not change.

iii)          Non- dimensional variables: These are variable quantities and have no dimensions example specific gravity, strain, angle etc. They are typically ratio of two similar physical quantities.

iv)           Dimensionless constants: These are mere numbers like 2, 3, 4, ∏ . The numeric value of dimensionless physical quantities remains unchanged in any system of units.

USE OF DIMENSIONAL EQUATION

Dimensional equation have following uses:

i)                 To check the correctness of a physical equation

It is based upon the principal of homogeneity of dimensions. According to this principle, the dimensions of all terms on two sides of a dimensional equation must be the same. The problem are solved by writing the dimensions of all terms on both sides of an equation.

4.Uncertainty in measurement and uncertainty in figures

Whenever you measure the value of some physical quantity using a measuring device, the precision of the result always depends on the instrument used. For example, if you measure the length of a tile with a measuring tape with

Marks at 1 cm interval, the result could be 10 cm. If you measure the same tile with a regular scale(marks at 1 mm interval) the result might be 10.1 cm. In the first case it is wrong to write 10.0 because it will misrepresent the limitation or precision of the measuring instrument. If you use a vernier caliper(of precision 0.1 mm) the result might be 10.16 cm. The differences between these three measurements is in their uncertainty, which reflects the precision of the measuring device. In the first case the uncertainty is 1 cm, in second it is 0.1 cm and in third case it is 0.01 cm. It tells that measurements with a vernier caliper has low uncertainty in comparison to measurement with a tape. Any measurements with it will have better