The Radar Detector Source

Posts Tagged ‘time interval’

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 3.0 x 10^9 Hz. The trap is set for cars travelling south. A motorist drives a car equipped with a radar detector along a east-west road that cross the main road at a level instersection 1.0 x 10^2 m [N] of the radar trap. The motorist hears a series of beeps upon driving west through the intersection. The time interval between successive quiet spots is 0.20s as the car crosses the main road. How fast is the car moving?

A police cruiser has an unusual radar speed trap set up. It has two transmitting antennae at the edge of a main road that runs north and south. One antenna is 2.0 m[west] of the other, and they are both fed from a common transmitter with a frequency of 3.0 x10^9 Hz. These antennae can be considered as point sources of continuous radio waves. The trap is set for cars travelling south. A student drives his car along an east-west road that crosses the main road at a level intersection 100 m[north] of the radar trap. The student’s car has a "radar detector", so he hears a series of beeps as he drives west through the intersection. If the time interval between successive quiet spots is 1/5 s, as he crosses the main road, what is his speed?