# physics

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A 200m dash along a straight track was timed at 21.1 s by a timer located at the finish line who used the flash from the starters pistol to start the stopwatch. If the air temperature was 30.0c , what would the time have been if the timer had started the watch upon hearing the sound of the gun.

• physics -

The speed of sound at that air temperature is about 345 m/s. The sound would not have arrived at the timer until 200/345 = 0.6s after the start of the race.

The recorded time would have been 20.5 s.

The delay due to the finite speed of light is negligible (about 1 microsecond).

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