A boy on a bicycle approaches a brick wall as he sounds his horn ...

[clippers!]

A boy on a bicycle approaches a brick wall as he sounds his horn at a frequency 400 Hz. The sound he hears reflected back from the wall is at a frequency 408 Hz.
 
  At what is the speed is the boy riding his bicycle toward the wall? Assume the speed of sound in air is 340 m/s.
  A)
 
  3.68 m/s
 
  B)
 
  333 m/s
 
  C)
 
  6.67 m/s
 
  D)
 
  6.80 m/s
 
  E)
 
  3.37 m/s

Question 2

A 55-cm steel rod has a diameter of 30 cm. The compressive strength of steel is 500  106 N/m2. What is the compression force that would break the rod?
 
  A)
 
  3.5  107 N
 
  B)
 
  2.4  107 N
 
  C)
 
  1.4  108 N
 
  D)
 
  4.7  108 N
 
  E)
 
  8.9  108 N

[jackie]

Answer to Question 1

E

Answer to Question 2

A

[clippers!]

Gracias!

[matt95]

Excellent