Physics hw

PS 115L

Homework 8

1

Name: ____________________

Date: _____________________

1. In St. Augustine there are alleged ghosts. During the night, there is an unknown frequency which

emits from unknown sources in the air. A scientist decides to investigate what the frequency is by

going near the source of the noise and holding a closed end tube (much like the one in the lab)

and measuring where the nodes are. The scientist hears higher frequencies at d110cm,

d2 = 28.2cm and d3 = 53cm. The measurements follow the diagram below:

a. What is the average of the wavelengths that the scientist found?

b. Using v = 340 m/s, and the average wavelength, what is the frequency the unknown sources emit?

PS 115L

Homework 8

2

2. The figure below shows water going through a pipe. The diameter of 𝐴1 is three times the

diameter of 𝐴2. What is true about the velocity of 𝑣1 𝑎𝑛𝑑 𝑣2? Show work which leads to the

correct answer.

a. 𝑣1 = 3𝑣2

b. 𝑣2 = 9𝑣1

c. 𝑣2 = 3𝑣1

d. 𝑣1 = 9𝑣2

PS 115L

Homework 8

3

3. Look at the following figure of the airflow apparatus (Venturi tube). The arrows represent airflow

inside a tube. With the information given and 𝜌𝑎𝑖𝑟 = 1.2𝑘𝑔/𝑚 3 ; 𝜌𝑓𝑙𝑢𝑖𝑑 = 1000𝑘𝑔/𝑚

3: Find 𝑣1,

𝑣2 𝑎𝑛𝑑 ∆ℎ.