In old times, before there were train signals, people who worked on the railroad would often put their ear down to the train track to listen for an oncoming train.

why would this result in hearing the train further off than just listening for the train through the air?

people did not do this because sound travels faster through less dense material, like air, rather than more dense materiel, like train tracks.

sound waves travel faster in more dense material, and the more dense the material the faster the sound is.

sound travels slower in air because there are often trees and other items blocking the sound.

sound travels slower, but louder through solid material because it is more dense, so the train could be heard better this way.

The wilson chamber is used to study: direction, speed, and distance of radioactivity the intensity of radiation the appearance of individual atoms all of the above

The earth's moon is unusually large. two popular theories of the moon's origin include the "sister world" hypothesis, which states that the moon formed from the same materials as the earth, near enough to the earth that they fell into orbit around each other. a second theory is the "capture" hypothesis, in which the moon formed elsewhere in the solar system, and the earth's gravity pulled it into its orbit. studies of what the moon is made of indicate that some of its materials had to come from the earth or from the same area of the solar system where the earth had formed. at the same time, the moon does not contain much of the material that makes up the earth's core, so the moon could not have formed from the same materials as the earth. how do the two facts above affect the described theories of the moon's origin? a. they show that scientists will never agree on where the moon came from. b. they show that more experiments on moon formation need to be done. c. they show that no theory accounts for the existence of the moon. d. they show that neither theory is complete and entirely correct.

What type of reaction is shown below? check all that apply. 2h2o2 → 2h2o + o2 synthesis decomposition combustion