Q.
According to Newton, the viscous force acting between liquid layers of area A and velocity gradient Δv/ΔZ is given by F=−ηAΔZΔv , where η is constant called coefficient of viscosity. The dimensional formula of η is
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AIPMTAIPMT 1990Physical World, Units and Measurements
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Solution:
Dimensions of force F=[MLT−2]
Dimensions of velocity gradient ΔZΔv=[L][LT−1] =[T−1]
Dimensions of area A=[L2]
Given F=−ηAΔZΔv
Dimensional formula for coefficient of viscocity η=(A)(ΔZΔv)F=[L2][T−1][MLT−2]=[ML−1T−1]