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How long, in minutes, do the picnickers have before the storm arrives at their location?

Picnickers see a lightning flash and hear the resulting thunder 9.0 s later. If the storm is traveling at a speed of 15 km/h, how long, in minutes, do the picnickers have before the storm arrives at their location? First, find how far, in km, the storm is initially and then calculate how much time, in minutes, it takes until the storm (moving directly towards the picnickers) arrives at their location.

Public Comments

1. Sound and light are produced simultaneously by the lightning strike. Since the sound takes 9 s to travel to the picnickers the storm is 9*v m away, where v is the speed of sound in air in the given conditions. Assume that to be 330 m/s. So the storm is 330*9 = 1980 m = 1.98 km away. At 15km/h, the storm can cover 1.98 km in 1.98/15 = 0.132 h = 7.92 minutes.