Select the correct answer.
Jenny and Fred both play a long note on their trombones. A stationary observer hears the sound increasing and decreasing repeatedly in loudness,
Which of these must be true?
A. The sound waves from the two trombones have slightly different frequencies.
B. The sound waves from the two trombones have the same frequency
C. The sound waves from the two trombones have slightly different amplitudes.
D.
The sound waves from the two trombones have the same wavelength,
E.
The sound waves from the two trombones have slightly different velocities.

Fill in the blank. the number of each type of element in the compound (other than 1) is represented by a small number to the right of the element symbol.

What is hidden during a lunar eclipse? isn't the moon hidden?

Samir watches a 100-minute movie on his spaceship. maria's spaceshipe flies in the same direction as samir's spaceship but she observes his move to last 125 minutes and his spaceship to be 40 m long. how long does samir observe his own spaceship to be? according to an observer on earth, planet x is stationary. maria and samir depart earth on their spaceships at the same time, each flying at 0.5c. maria flies toward planet x and samir flies in the opposite direction. according to maria, her voyage to planet x takes 9 years. how many years does marias voyage take according to samir?