Can someone me with a question on my a car's horn sounds different as the car approaches. the change in pitch is due to
i am pretty sure the answer is the doppler effect, but i just wanted to check if i was right? the other answer choices are electromagnetism, the absorption of sound, the creation of a vacuum.

If a 20.0ml test tube measures 15.0cm, what is the length in meters?

In the haber reaction, patented by german chemist fritz haber in 1908, dinitrogen gas combines with dihydrogen gas to produce gaseous ammonia. this reaction is now the first step taken to make most of the world's fertilizer. suppose a chemical engineer studying a new catalyst for the haber reaction finds that 671 liters per second of dinitrogen are consumed when the reaction is run at 271c and 0.99atm. calculate the rate at which ammonia is being produced. give your answer in kilograms per second. round your answer to significant digits.

The atomic number of an element is based on the number of electrons around its core mass of its nucleus number of protons in its nucleus number of neutrons in its nucleus