A stationary speed gun emits a microwave beam at 2.1*10^10Hz. it reflects off a car and returns 638hz lower. what is the speed of the car?
- NCSLv 77 months ago
Because the speed of the car is orders of magnitude less than the speed of the radar, we can use the Doppler simplification
(f₀ - f) / f₀ = 2v / c
638 / 2.1e10 = 2v / 3e8m/s
which solves to
v = 4.6 m/s
Hope this helps!
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