The terminal velocity of a copper ball of radius `2mm` falling through a tank of oil at `20^(@)C` is `6.5cm//s`. Find the viscosity of the oil at `20^(@)C`. Density of oil is `1.5xx10^(3)Kg//m^(3)`, density of copper is `8.9xx10^(3)Kg//m^(3)`.

Explanation

To find the viscosity of the oil at 20°C given the terminal velocity of a copper ball falling through it, we can use Stokes' law. Here’s the step-by-step solution:

### Step 1: Understand the Problem
We have a copper ball falling through oil, and we need to find the viscosity of the oil using the given terminal velocity, radius of the ball, and densities of both the ball and the oil.

### Step 2: Write Down the Given Data
- Radius of the copper ball, \( r = 2 \, \text{mm} = 2 \times 10^{-3} \, \text{m} \)
- Terminal velocity, \( V_T = 6.5 \, \text{cm/s} = 6.5 \times 10^{-2} \, \text{m/s} \)
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