Some areas of the country do throw the weight in youth competitions. If you or one of your athletes is scheduled to throw in a youth meet, you will need to contact the meet director and check what size weight they will be using for the age group.
In the sense of performing as designed, most radar detectors do detect the presence of police radar in the immediate vicinity of a speeding vehicle. Whether or not that information will actually prevent a driver from receiving a speeding ticket remains to be seen, however.
Scientists use a form of visible radar called lidar (light detection and ranging) to measure air pollution with lasers. Archeologists and geologists point radar down into the ground to study the composition of the Earth and find buried deposits of historical interest. One place radar isn't used is on board submarines. Electromagnetic waves don't travel readily through dense seawater (that's why it's dark in the deep ocean). Instead, submarines use a very similar system called SONAR (Sound Navigation And Ranging), which uses sound to see objects instead of radio waves.