Next, given the speed of sound at 20 °C is approx. 343.6m/s the sound lag at 2m would be approx 5.82ms or at 1m would be approx 2.91ms
Given the shutter lag is 40ms then at 2m the total lag time is approx 45.82ms, the cork would travel 50.4cm or if we place the microphone at 1m the distance would be 47.5cm. The microphone could be placed closer.
Of course this doesn't take into account the lag in the trigger circuit and even if you use a laser detector there is a lag in the circuit. But even if this were instantaneous you would have the shutter lag of 40ms and at 40km/h the cork would travel 44cm.