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Finding Average Velocity

A safety devi...

Question

A safety device brings the blade of a power mowerfrom an initial angular speed of w₁to rest in 1 revolution. At the same constant acceleration, how many revolutions would it take the blade to come to rest from an initial angular speed w₃ that was three times as great, w₃=3w₁

please answer me clearly so that I can understand well.

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Solution

The resistive force of any object rotating about an axis varies as the square of the angular speed,

Therfore, the number of revolution required will be 9..

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In one revolution the distance covered is 2π,
so, in 5 revolution the distance moved is 10π
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So using equation,
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Why my Answer is different? Where and what I am missing.
NOTE : I can't write omega on my tablet also you understand it well that we can type only that which is given in keyboard.

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