



 
Hi, You didn't say what units to use so I am going to show you how to express angular speed radians per second. 2 revolutions in 4 seconds is 1 revolution in 2 seconds or half a revolution in 1 second. There are $2 \pi$ radians in one revolution so that's \[\frac12 \times 2 \pi = \pi \mbox{ radians per second.}\] Penny  


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