một cái còi đứng yên phát ra sóng âm có tân số 1000Hz, lấy tốc độ truyền âm trong không khí là 330m/s. Một người chuyển động ra xa cái còi với tốc độ 36km/h. Tần số mà người này nghe được trực tiếp từ còi phát ra là

You are traveling in a car going at a constant speed of 100km/h down a long, straight highway. you pass another car going in the same direction which is traveling at a constant speed of 80km/h. as measured from your car's reference frame this other car is traveling at −20km/h. what is the acceleration of your car as measured from the other car's reference frame? what is the acceleration of the other car as measured from your car's reference frame?

An insulated 40 ft^3 rigid tank contains air at 50 psia and 120°f. a valve connected to the tank is now opened, and air is allowed to escape until the pressure inside drops to 25 psia. the air temperature during this process is kept constant by an electric resistance heater placed in the tank. determine the electrical work done during this process.

What is the single most important equation in all of physics?