[Answer is V = 25m/s, however, how do I get that answer? Thank you!] A police cruiser sets up a novel radar speed trap, consisting of two transmitting antennas at the edge of a main north-south road. One antenna is 2.0 m [W] of the other. The antennas, essentially point sources of continuous radio waves, are fed from a common transmitter with a frequency of 9 3.0 10 ^9 Hz . The trap is set for cars travelling south. A motorist drive a car equipped with a “radar detector” along an east-west road that crosses the main road at a level intersection 100 m [N] of the radar trap. The motorist hears a series of beeps upon driving west through the intersection. The time interval between succesive quiet spots is 0.2s as the car crosses the main road. How fast is the car moving?
The Attempt at a Solution
Unfortunately I cannot figure out a way to get V = 25 m/s, however that is the answer. It seems as though there are too many unknowns. Any help would be appreciated, thank you.