A simple way to say how fast a U.C.M. is going is to express how long it takes to make a complete circuit.

  1. How long does it take the second hand of a clock to make a complete circuit?  
  Another way of expressing the speed of a U.C.M. is to say how many circuits it makes in one minute.

  2. How many circuits does the second hand of a clock make in one minute? (r.p.m.)
   You can also calculate the number of circuits made in one second. 

  3. How many circuits does the second hand of a clock make in one second? (r.p.s.)
   You can repeat the exercise for the other two hands of the clock.