At a sudden contraction in a pipe the diameter changes from D1 to D2. The pressure drop, ?p, which develops across the contraction is a function of D1 and D2, as well as the velocity, V, in the larger pipe, the fluid density, ρ, and viscosity,µ. Use D1, V, and µ as repeating variables to determine a suitable set of dimensionless parameters. Why would it be incorrect to include the velocity in the smaller pipe as an additional variable?