Question

The angle between viscous force and direction of flow of liquid

Answer 1

The Navier-Stokes equations then become:

ρ[∂v⃗ ∂t+(v⃗ ∇⃗ )v⃗ ]=−∇⃗ p+ηΔv⃗ +f⃗

and are simplified to:

0=η∂2v∂y2+ρgx

where gx=ρgsinθ with g the gravitational constant.