Imagine that at a certain place in a river, water moves horizontally to the left. Consider an oriented sur-face that faces in a direction that is $30^{\circ}$ upward of right. The flux of water velocity $\vec{v}$ through this surface is

Question

Quizplus · Accepted Answer

The flux is negative because the water is moving to the left, while the surface is oriented upward to the right. The angle between the velocity vector and the surface normal is greater than $90^{\circ}$, resulting in a negative dot product and thus a negative flux.

Imagine That at a Certain Place in a River, Water 30∘30^{\circ}30∘

Imagine That at a Certain Place in a River, Water $30^{\circ}$