Define Stoke’s law. Define and derive an expression for terminal velocity.

Explanation

### Step-by-Step Solution

**Step 1: Define Stokes' Law**
Stokes' Law describes the motion of a small spherical object moving through a viscous fluid. It states that the viscous drag force \( F \) acting on a small spherical body of radius \( r \) moving with a velocity \( v \) through a fluid of viscosity \( \eta \) is given by the formula:
\[ F = 6 \pi \eta r v \]
This equation indicates that the drag force is directly proportional to the velocity of the object, the radius of the object, and the viscosity of the fluid.
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