A body dropped from a height H reaches the ground with a speed of 1.2 `sqrt(gH)`. Calculate the work done by air friction.

Explanation

To solve the problem of calculating the work done by air friction on a body dropped from a height \( H \) that reaches the ground with a speed of \( 1.2 \sqrt{gH} \), we can follow these steps:

### Step 1: Identify the initial and final kinetic energy
- The initial kinetic energy (\( KE_i \)) of the body when it is dropped from height \( H \) is \( 0 \) (since it is at rest).
- The final kinetic energy (\( KE_f \)) when it reaches the ground can be calculated using the speed given:

\[
KE_f = \frac{1}{2} mv^2
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