Final answer:
The difference between Josh's record and practice times is approximately 0.3 seconds. The coach's new stopwatch with an uncertainty of ±0.05 seconds may have limitations in timing very close sprint finishes.
Step-by-step explanation:
The difference between Josh's record time and his practice time is the subtraction of the two times: 65.56 seconds minus 65.29 seconds. The calculation gives us a result of 0.27 seconds. A reasonable estimate for the difference in times would be about 0.3 seconds, as this is close to the actual difference and is a simple, rounded number that is easily communicated.
Furthermore, regarding the high school track coach's new stopwatch, which has an uncertainty of ±0.05 seconds, it would be somewhat useful. In sprints, where the differences in times are often very small, the uncertainty can be significant. For instance, the difference between the first and second place sprinters at the track meet was 12.07 seconds minus 12.04 seconds, which is 0.03 seconds. This difference is smaller than the uncertainty of the stopwatch itself, which means that the stopwatch may not be able to reliably distinguish between runners with such close sprint times.