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Using rotational kinematic formulas

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A fan initially rotates clockwise at 9.0rads, but has a counterclockwise angular acceleration of 3.0rads2 and reaches a counterclockwise angular speed of 27rads.
How much time did this change in the angular velocity take?
Answer using a coordinate system where counterclockwise is positive.
Round answer to two significant digits.
  • Your answer should be
  • an exact decimal, like 0.75