2-80.  In 1991, Carl Lewis set a new world record of 9.86 s for the 100-m dash. His “split times” for various parts of the 100 m distance were as follows (Data based on R. Myers, The Physics Teacher, 30, 89, 1992):

0 to 10 m 1.88 s 50 to 60 m 0.84 s 10 to 20 m 1.08 s 60 to 70 m 0.84 s 20 to 30 m 0.92 s 70 to 80 m 0.83 s 30 to 40 m 0.89 s 80 to 100 m 1.73 s 40 to 50 m 0.84 s

a.   Why did the first 10 m take the longest time? b.   During which 10-m stretch was his average acceleration greatest? Estimate its value, and state any assumptions you make in doing your calculation.

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