An alert physics student stands beside the tracks as a train rolls slowly past. He notes that the frequency of the train whistle is 493 Hz when the train is approaching him and 476 Hz when the train is receding from him. Using these frequencies, he calculates the speed of the train. What value does he find

the answer would be c. motion and direction

i hope this : )

massxgravity x heght=weightxheight= pe

4900=490xh

h=10

answer;

d. are made mostly of liquid

explanation;

-the general   composition and structure planets includes; they have a thick gas and liquid layer covering a small,solid core. mostly the gases are hydrogen and helium atmosphere and layers of liquid hydrogen. for instance neptune and uranus are examples of the outer planets, they have a core covered by ice and ammonia.

-neptune's atmosphere is hydrogen and helium with a bit of methane so there is no oxygen to breath and the interior is made up of frozen water and ammonia with a rock and iron core. thus, there is no liquid water or solid surface to survive.