The law in which models are based on weber's number is called as weber's model law

When ever surface tension forces are predominant as compare to other forces for dynamic similarity weber number in model must be equal to weber number in prototype

$w_{m}=w_{p}$

$\frac{v_{m}}{\sqrt{\frac{\sigma_{m}}{p_{m}L_{m}}}}=\frac{v_{m}}{\sqrt{\frac{\sigma_{p}}{p_{p}L_{p}}}}$

Weber's model law is applicable in following case

(i) Capillary movement of water in soil

(ii) study of droplet, study of very small jet

(iii) Capillary waves in channel

(iv) flow over weirs for small heads

Mach model law

The law in which models are based on mach number is called mach model law

whenever elastic forces are predominant as compared to other forces, for dynamic similarity Mach number in the modal law mus the equal to mach number in prototype

Mmodel= Mprototype

$\frac{v_{m}}{\sqrt{\frac{k_{m}}{p_{m}}}}=\frac{v_{p}}{\sqrt{\frac{k_{p}}{p_{p}}}}$

where K=Elastic stress

Mach model law are applicable in following case

i) flow of aeroplane of supersonic speed

ii) underwater testing to torpedoes

iii) Aerodynamic testing

iv) flow of missiles rockets

v) water hammer problem