Kyoko asked in Science & MathematicsPhysics · 7 months ago

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?

1 Answer

  • NCS
    Lv 7
    7 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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