Define dimensional formula. What are the uses of dimensional analysis ?
Deduce the dimensional formula for
(a) Pressure
(b) Power
Answers
The dimensional equations have got following three uses: To check the correctness of a physical equation. To derive the relation between different physical quantities involved in a physical phenomenon. To change from one system of units to another.
Pressure=M1 L-1 T -2
Power=kg⋅m2⋅s−3
Answer: Dimensional Formula is the expression which shows how and which of the base quantities represent the dimensions of a physical quantity.
Uses/Applications of Dimensional Analysis: 1. Checking Dimensional Consistency of equations
- A dimensionally correct equation must have same dimensions on both sides of the equation.
- A dimensionally correct equation need not be a correct equation but a dimensionally incorrect equation is always wrong. It can test dimensional validity but not find exact relationship between the physical quantities.
2. Deducing relation among physical quantities
- To deduce relation among physical quantities, we should know the dependence of one quantity over others (or independent variables) and consider it as product type of dependence.
- Dimensionless constants cannot be obtained using this method.
Dimensional Formula for: (a) Pressure= Force = Mass x Accelaration
Area Area
= Mass x Distance = Mass x Length = M.L = ML = ML. L^-2T^-2
Area x Time^2 Length x Time^2 L^2.T^2 L^2T^2
= ML^-1T^-2.
(b) Power= Work = Force x Distance = Force x Length = MLT^-2. L
Time Time Time T
= ML^2T^-2 = ML^2T^-2. T^-1 = ML^2T^-3.
T
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