A fixed viscosity and gap turn speed differences into checked stress rows. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Four metres per second over four metres gives one per second
Viscosity stays 4 Pa*s. Speed difference 4 m/s over gap 4 m gives stress 4 Pa.
4⋅4/4=4
Eight metres per second doubles the stress
The gap and viscosity remain fixed. Speed difference 8 m/s gives stress 8 Pa.
4⋅8/4=8
Twelve metres per second gives twelve pascals
Speed difference 12 m/s makes shear rate 3 reciprocal seconds and stress 12 Pa.