Physics- Velocity

Question

1. While at a track meet, you notice a time delay between when you see the starter’s pistol fire and when you hear it. If that delay is 0.4 seconds, how far away are you? Draw a picture of the situation.

Answer 1

The light from the pistol firing reaches you with imperceptible delay (after all, light from the Sun at 1.5 x 10¹¹ m takes only 8 minutes to get here). So the delay is due to the relatively slow speed of sound. Apparently they gave you no value to use for this -- it does depend on temperature. If we take the usual value of 343 m/s, then your distance from the pistol is about d = v t ≅ (343 m/s) (0.4 s) ≅ 140 m.