I’ve heard that a speed gun uses the Doppler effect to do some calculation and get the speed of a car, but can it work on multiple vehicles at the same time? How is it possible?
In: Physics
It would be technically trivial to make a speed gun measure multiple vehicles at once, but for practical and legal reasons it is important to show that the measured speed was off just one specific vehicle. So most (maybe all) just measure one at a time, though they automatically store the readings and can measure several vehicles in quick succession. So a cop might measure a line of vehicles individually, then radio each speed with a description of each corresponding vehicle to his colleague at the stop post a little ways down the road.
Recent generation speed guns capture picture evidence when measuring, so there’s never any doubt as to what car the gun was aimed at.
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