An electric ceiling fan with blades of diameter 0.710m is rotating about a fixed

Question

An electric ceiling fan with blades of diameter 0.710m is rotating about a fixed axis with an initial angular velocity of 0.280rev/s . The angular acceleration is 0.886rev/s2.

A) Compute the angular velocity after a time of 0.197s . Round to four signifigant figures. I tried 0.28+(0.866)(0.197) = 0.450602....four sig figs would be 0.4506. For some reason this answer is incorrect. I also tried 0.45 and 0.451 just to see if they would work and they didn't work as well. Am I using the wrong formula? I used: angular velocity = angular velocity initial + (angular acceleration)(time)   

Explanation / Answer

This is a silly error many commit

0.28+(0.866)(0.197) = 0.450602

Here you put w = 0.280 which is wrong since it is given in rev/sec

Convert it to rad / s

w= 0.280 * 2*3.14 rad / sec ------------since 1 revolution = 2 * 3.14 rad

we get ,

w = 1.7854 rad / sec

Final angular velocity = Answer you got * 2* 3.14 = 2.82978 rad / sec

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