I wish everyone a great summer and good luck in the future.

Mr. Hamilton

• Energy Review
• Sound, Waves and Projectile Motion

1. Read Section 12.2:  Electric Fields and Electric Charge on pages 432 to 435.
2. What is an electric field?
3. State Coulomb’s Law in words and as an equation.
4. With the aid of a diagram, explain how Milikan’s Oil Drop Experiment allowed him to find the charge on an electron.
5. Do Lab Exercise:  12.2.1:  Investigating Data from Millikan’s Oil Drop Experiment on page 434.
6. Do #1 and 2 on page 435.

– Post From My iPhone

The class then looked at the Doppler Effect which is the apparent change in frequency due to the relative motion of the source of the sound and an observer of the sound.  The Doppler Effect can be noticed when a speeding Fire Engine with a siren blaring passes by a bystander.

The formula for the Doppler Effect is

where v is the velocity of sound and v_s is the speed of the sound source relative to the observer.  The negative is used when the source is moving towards the observer.

The students did #1 and 2 on page 269 and #2 on page 272 for homework.

After the test, the students did the following:

1. Read Section 7.2:  Electric Current  on pages 319 to 322.
2. Define the following terms:
   1. Electric current
   2. Ampere
   3. Direct Current
   4. Alternating Current
   5. Conventional Current
   6. Electron Flow
3. What is the typical current of the following:
   1. Battery Powered Wristwatch
   2. Battery Powered Calculator
   3. Flashlight
   4. Electric Drill
   5. Oven Element
   6. Toaster
   7. Car Starter Motor
4. Do #2 on page 320
5. Do #4, 6 on page 322.

• Beat Frequency:  Mr. Hamilton struck two tuning forks that were at slightly different frequencies.  The sound of the two tuning forks got louder and quieter.  A microphone was connected to a computer with Zelscope, a program that simulates an oscilloscope.  When the two tuning forks were struck, the resulting wave got larger and smaller.
• This getting larger and smaller is the Beat Frequency.
• B.F. = Absolute Value( frequency 1 – frequency 2)
• Sonic Booms:  When objects go faster than the speed of sound, the sound from a number of different locations reaches an observer at the same time.  This creates a sonic boom.

The following work was assigned:

1. Read Section 7.9:  Beat Frequency on page 264 to 266.
2. Do questions #3, 5, and 7 on page 267.
3. Read Section 7.10:  The Doppler Effect and Supersonic Travel on pages 267 to 272.
4. Do question #1 on page 273.

I managed to get the tuning forks to be just about the same frequency.  I couldn’t detect a beat frequency, so don’t move the masses for the first demonstration.

To demonstrate Mechanical Resonance using Columns of Air, place the two tuning forks with the open ends pointing at each other and the boxes a couple of feet apart.  Strike on tuning fork and then place your hand on that tuning fork one or two seconds after you have stricken the tuning fork.  If the students are quiet, you should be able to hear the other tuning fork is now vibrating in sympathy with the first tuning fork.

You can then move the tuning forks farther apart until they are on opposite sides of the room.

After you do this, you can move the masses a couple of milimetres which will change the frequency.  With a slightly different frequency, you can hear the Beats where the volume goes up and down.  The formula for the Beat Frequency is:

Beat Frequency = |f₁-f₂|

As the absolute value is used, if the beat frequency is known and one of the two frequencies is also known, the other frequency cannot be determined to one value.  It can only be determined to be two possible values.  However, by making another slight change and noticing an increase or decrease in the Beat Frequency.

You can remind the period 5 class of the formula for the beat frequency.  Some of the homework questions concern the beat frequency.

You can show the following videos on the Doppler Effect and Sonic Boom.  The first one gives a fairly good explanation of the Sonic Boom and the visible cone around the plane as it breaks the sound barrier.

Doppler Effect

The first video is a nice example of the Doppler Effect with a fire engine passing by an observer.

http://www.youtube.com/watch?v=imoxDcn2Sgo

The second video uses animation to explain the Doppler Effect.

http://www.youtube.com/watch?v=RsiY8VdDlDQ

Sonic Boom

http://www.youtube.com/watch?v=-d9A2oq1N38&feature=related

http://www.youtube.com/watch?v=QjpikTn2qAk&feature=related

The second video is a short clip of a fly-by for a military jet breaking the sound barrier.

You have to go over the formula for the Doppler Effect

Remind them that v_s is the speed of the source and not the speed of sound.    You also have to teach them how to determine the Mach number (speed of object/speed of sound)

You can assign the following questions:

1. #1, 2, 3, 4, 5 on pages 266 to 267.
2. #1 and 2 on page 269.
3. #3, 4, 5 on page 270
4. #1, 2, 3, and 5 on page 272.

The class also went over the article, “Dangerous Decibels.”  These questions look at the causes of hearing loss and focuses on Noise Induced Hearing Loss.  NIHL is caused by being exposed to sound louder than 85 dB for more than 8 hours per day.

The students read Section 7.6:  The Reflection of Sound on pages 254 to 257 and did the following:

1. Describe how the following work:
1. sonar
2. echolocation
3. Medical Ultrasound

• Hearing
• Decibel scale
• Converting from decibels to W/m²
• The Human Ear
• Parts of the Ear
• Function of the Ear
• Hearing loss through exposure to loud noises
• Limits on time to be exposed to loud noises

Sound Intensity is usually measured in deciBels.  To convert from dB to W/m² and back.

number of dB = [ log(number of W/m²) + 12] × 10

number of W/m² = 10 to the exponent [ (number of dB ÷ 10) - 12]

The students read an article on noise and hearing loss.  The article can be found at the following website:

http://www.dangerousdecibels.org/hearingloss.cfm.

The students answered questions on this article and the question sheet can be found here.

After answering the questions, the students did the following:

• Read Section 7.5:  The Human Ear on pages 249 to 253.
• Draw (or trace) and label the Parts of the the Human Ear using the diagram on page 250.
• Describe the structure and function of the following parts of the Human Ear:
  • Auditory canal
  • Eardrum
  • Hammer, Anvil, and Stirrup
  • Cochlea
  • Auditory nerve
  • Eustachian tube

Here are the questions.

Dangerous Decibels:  About Hearing Loss

1)       What drugs can cause hearing loss with prolonged use?

2)       Describe what causes the following types of hearing loss and outline how it affects hearing:

a)       Meniere’s Disease

b)       Trauma

c)       Presbycusis

d)       NIHL (Noise Induced Hearing Loss)

3)       What happens in the ear that causes NIHL (Noise Induced Hearing Loss)?

4)       What is the lowest decibel level that some people are able to hear?

5)       What happens if people are exposed to decibel levels higher than 85 dB?

6)       How loud is a typical conversation?

7)       How loud are earphones at a standard volume of 5?

8)       According to the table in this article, how long can someone be exposed to the following decibel levels without experiencing hearing loss:

a)       88 dB

b)       91 dB

c)       94 dB

d)       100 dB

e)       109 dB

9)       Compare these values to the table duration of exposure to sound levels from the Ontario regulations under the Occupational Health and Safety Act.

When they have finished the review, the students did the following work.

1)      Do the Are You Ready? Questions on pages 312 and 313.  This is a diagnostic test to see how much they already know about electricity and electric currents.

2)      Read Section 7.1:  Electrical Circuits on pages 316 to 318.

3)      Do questions #1, 2, 3, and 4 on page 317.

4)      Do questions #1 and 2 on page 318.

You can download a copy of the review by clicking here.

Hydraulics and Aerodynamics Review

1.  State the following laws in complete sentences:
a.  Pascal’s Principle

b.  Bernoulli’s Principle

2.  Find the density of the following objects and use the table on page 223 to determine the
substance:
a.  100 mL of a liquid has a mass of 79 g.
b.  A cylinder has a height of 12 cm, a diameter of 2.5 cm and a mass of 463 g.

3.  Find the mass of copper if copper has a density of 8.95 g/cm³ and the block has dimensions of 3.4
cm by 5.2 cm by 9.0 cm.

4.  Find the pressure for the following situations:
a.  Find the pressure if 350 N of force is exerted on an area of 2.5 m².

b.  Find the pressure exerted on the floor if a 75 kg box has a length of 2.5 m and a width of
1.2 m.

5.  Find the total force exerted by the following:
a.  Find the force exerted if the pressure is 75 Pa and the total area is 2.5 m².

b.  Find the force exerted if the pressure is 101.3 kPa and the area is 0.75 m².

6.  What is the absolute pressure if a pressure gauge reads 75 kPa and the atmospheric pressure is
101.3 kPa?

7.  Use a diagram to show how the following devices work:
a.  Barometer
b.  Aneroid Barometer
c.  Hydraulic Press

8.  Describe what happens to the pressure if you increase your depth underwater.

9.  Why is the change in pressure with depth important to people or things that are underwater?  You
can talk about a scuba diver or a submarine.

10.  What is the force exerted by a hydraulic press is a force of 75 N is applied to on end that has an
area of 5.0 cm².  The other end of the press has an area of 22.5 cm².

11.  What would be the weight of an object that has a volume of 25 cm³ and has a weight (force of
gravity while it is out of the water) of 310 N?

12.  Use Bernoulli’s Principle to explain what happens when a hurricane blows strong winds over a
house.

13.  Use Bernoulli’s Principle to explain how a carburetor or a spray bottle works.  Use a diagram to
help your explanation.

14.  Describe how streamlining and aerodynamics are used by race car designers to improve the
performance of the car.

The class also looked at the sound intensity and measured the number of decibels in the classroom.

The students were assigned the following work:

1. Read Section 7.5:  The Human Ear on pages 249 to 253.
2. Do questions #1 and 3 on page 253.

After this, the class looked that the factors that affect how planes fly.  The students then used the Airplane Design Workshop website to try to design an airplane to carry 200 passengers from Washington, D.C. to another city.  This website can be found at http://edu.larc.nasa.gov/connect/model/norbert/adw/adw.html.

The following was assigned for homework.

Page 295 #3, 4, 5, and 8

Page 296 #1, 2, 5

The change in time was determined, and the speed was found.  This speed was compared to the accepted speed of sound using the temperature of the air and the formula.

The following work was assigned for homework:

1. Do questions #3, 4, 5, 6, 7, and 9 on page 246.
2. Read Section 7.4:  The Intensity of Sound  on pages 247 and 248.
3. Define the decibel.

The Bernoulli Principle states that where a fluid is flowing quickly, the pressure is low, and where the fluid is moving slowly, the pressure is higher.

The Bernoulli Principle allows planes to fly and paint sprayers to work.

The students did the Try This Activity:  Paper Airplanes  on page 292.  There will be a contest on Wednesday to find the airplane that flies the farthest.