9 Question 21 (5 points) a) What is the frequency, in hertz, of Earth revolving around the Sun? Assume it 12 takes exactly 365 days for 1 revolution. (2 marks) 15 b) Derrick is discussing physics with Erin and says, "Sound travels faster through colder air because colder air is more dense." Erin disagrees and says, "That is not true. Sound travels faster through warmer air 18 because the molecules are moving faster." Who is correct? Explain. (2 marks) 21 c) The speed of sound in glass is 5170 m/s. A glass block is used as a percussive instrument and has a frequency of 4120 Hz. What is the wavelength of the sound in the glass? (1 mark) DII Paragraph V BIUA Ev v +