Two trains on separate tracks are moving towards each other. Train 1 is moving with a speed of 120 km/h and train 2 with a speed of 80 km/h. Train 2 blows its horn, emitting a frequency of 500 Hz. What is the frequency heard by the engineer on train 17 (hint: use speed of sound in air as 340m/s) ​

Aspecial electronic sensor is embedded in the seat of a car that takes riders around a circular loop-the-loop ride at an amusement park. the sensor measures the magnitude of the normal force that the seat exerts on a rider. the loop-the-loop ride is in the vertical plane and its radius is 23 m. sitting on the seat before the ride starts, a rider is level and stationary, and the electronic sensor reads 740 n. at the top of the loop, the rider is upside down and moving, and the sensor reads 370 n. what is the speed of the rider at the top of the loop?

With i really need the correct answer!

What makes thermal imaging cameras useful? they can detect differences in color. they can detect differences in wave speeds. they can detect differences in temperature. they can detect mechanical waves.