Starting from rest, a fan takes five seconds to attain the maximum speed of 400 rpm (revolutions per minute). Assuming constant acceleration find the time taken by the fan in attaining half the maximum speed.

Explanation

To solve the problem step by step, we will use the concepts of angular motion and the equations of motion for constant angular acceleration.

### Step 1: Understand the given data
- The fan starts from rest, so the initial angular velocity (\( \omega_0 \)) is 0.
- The final angular velocity (\( \omega_f \)) is 400 rpm.
- The time taken to reach this maximum speed is 5 seconds.

### Step 2: Convert the final angular velocity from rpm to rad/s
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