Question

Define coefficient of viscosity. State its formula and S.I. units.

Hint:

Viscosity is important in determining how easily a fluid flows. High viscosity fluids like honey resist motion, while low viscosity fluids like water flow easily.

Answer 1

Step 1: Definition.
The coefficient of viscosity \( \eta \) describes the internal friction in a fluid as it resists the motion of its layers. A higher viscosity indicates a thicker fluid that resists motion more, while a lower viscosity indicates a thinner, more fluid substance.
Step 2: Formula.
The formula for the coefficient of viscosity is given by: \[ \eta = \frac{F}{A \cdot \frac{v}{x}} \] This relationship shows that viscosity depends on the applied force, the area through which the fluid flows, and the velocity gradient.
Step 3: S.I. Units.
The S.I. unit of viscosity is the pascal-second (Pa·s), which can also be written as \( \text{N} \cdot \text{s/m}^2 \). This unit represents the force per unit area needed to produce a certain velocity gradient in the fluid.