Two copper balls of radius r and 2r are released at rest in a long tube filled with liquid of uniform viscosity. After some time when both the spheres acquire critical velocity (terminal velocity) then ratio of viscous force on the balls is :

Options

A. `1:2`
B. `1:4`
C. `1:8`
D. 1:18`

Explanation

To solve the problem, we need to find the ratio of the viscous forces acting on two copper balls of different radii when they reach terminal velocity in a viscous liquid.

### Step-by-Step Solution:

1. **Identify the Forces Acting on the Balls:**
Each ball experiences three forces:
- The gravitational force (\(F_g\)) acting downwards.
- The buoyant force (\(F_b\)) acting upwards.
...