27 rain drops of radius 1 mm each are falling down with a terminal velocity of 4 cm/s. They then coalesce to form a bigger drop. Determine the radius of bigger drop.

Explanation

To determine the radius of the bigger drop formed by the coalescence of 27 smaller raindrops, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the radius of the smaller raindrops**:
The radius \( r \) of each raindrop is given as 1 mm. We convert this to meters for consistency in units:
\[
r = 1 \text{ mm} = 1 \times 10^{-3} \text{ m}
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