Practice portal › Units and Measurements › Deriving Relations by Dimensional Analysis
Asked in AIPMT 2015 · Deriving a relation by dimensional analysis
[η]=[ML⁻¹T⁻¹], [ρ]=[ML⁻³], [γ]=[L]
[v_c]=[LT⁻¹]=[ML⁻¹T⁻¹]^x[ML⁻³]^y[L]^z
Idea: match the exponents of M, L and T one at a time.
Time: -x=-1⇒ x=1
Mass: x+y=0⇒ y=-1
Length: -x-3y+z=1⇒ -1+3+z=1⇒ z=-1
So x=1, y=-1, z=-1, giving the familiar v_c=(kη)/(ργ).
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