Author: Lee Trampleasure

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2/20 PotU: More on earthquakes and tsunamis

image showing earthquake strengths in Japan

Warm up

What is the name of the wave that was destructive after the Japanese earthquake? Are we at risk of a significant one if we have an earthquake on the San Andreas Fault?

Answer

There were two possible correct answers to this warm up:

(1) The Tsunami (a wave of ocean water) caused extreme damage to low-lying ares along the Japanese coast. At VHS, we are not at a significant tsunami at VHS because (a) Even through we are at a relatively low elevation, we are far from the ocean (the wave would have to come through the Golden Gate, then work its way up the Carquinez Straights, and (b) The San Andreas fault in California is a strike-slip fault, and these do not tend to cause large tsunamis.

(2) Some students answered the secondary wave, remembering that the primary waves tend to cause less damage than the primary waves. We are at risk of damage from secondary waves from earthquakes at VHS, but not nearly as much since we are further away from the fault.

Class work

Review earthquake/tsunami worksheet. Make sure you turn them in if you did not give to sum.

Note: The Richter scale is logarithmic, which basically means that for every number increase, the earthquake was ten times bigger. For example, a 7 is ten times bigger than a 6, and an 8 is 100 times bigger than a 6.

Short pseudoscience video

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2/19 AP: More momentum problems.

photo showing cue ball breaking a triangle of billard balls

It looks like I’ll be back on Thursday. Still a rough throat, but the doc thinks I’ll be ready by then. I’ll probably have a wireless mic so I don’t have to strain my voice 😊 .

You might also find these instruction helpful.

Problem 25, Page 183

I hope to post some videos showing how to solve yesterday’s assigned problems, but here are a few others that might be helpful.

Elastic collisions
Elastic vs inelastic collisions.
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2/19 PotU: More about earthquakes

Warm up

Describe a tsunami, when they occur, and why they can be so destructive.

It looks like I’ll be back on Thursday. Still a rough throat, but the doc thinks I’ll be ready by then. I’ll probably have a wireless mic so I don’t have to strain my voice 😊 .

Today’s work

Read through the earthquake pamphlet and complete the worksheet. Remember to reflect on about both energy and waves as you complete the earthquake packet. That’s what earthquakes are all about.

Resources

Reading pamphlet

Worksheet

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2/18 PotU: Japan’s Killer Quake, March 11, 2011

Warm Up

Which has more momentum? A huge truck stopped in the parking lot or a bee flying towards you? Explain why.

Classwork

Today and tomorrow and tomorrow we will look at earthquakes.

Today’s video: Japan’s Killer Quake, by NOVA

Https://www.pbs.org/wgbh/nova/videos/japans-killer-quake

As you watch this video, please hold in your hearts the 230,000 people who died from the earthquake and tsunami.

Worksheet assignment

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Other notes from today’s video

image showing strength of 2011 Tohoku earthquake
  • Earthquake ‘P’ waves travel about 1-14 km/sec.
    • P stands for primary since they arrive first.
    • These waves are longitudinal/compressional waves.
  • ‘S’ waves travel at about 1-8 km/s, and are the more damaging ones.
    • S stands for shear, but also for secondary (since the arrive second)
    • These waves are transverse waves.
  • The earthquake struck about 60 miles off the coast.
  • Warnings on all cell phones across Japan. The US is developing this warning system for the west coast.
  • In the nuclear power plant that was damaged, nuclear energy (stored in uranium) is converted to thermal energy, then to kinetic energy, then to electrical energy.
  • Waves reach Tokyo 100 seconds after the Quake, city had one minute warning. Earthquake lasted for five minutes in Tokyo
  • Liquefaction is when moisture in earth is compressed and squeezed out–sort of like squeezing a sponge.
  • Tsunami was about 3 feet high, 60 miles in length.
  • Tsunami can travel over 500 MPH.
  • In the ocean, the wave is not ‘cresting.’ Just like normal waves, they usually crest as they reach short.
  • Wavelength of the tsunami was long.
  • ‘Miyaku’s high walls are useless’ True or not true?
    • Land dropped up to three feet in some places. This made the walls less useful, but it still decreased the damage.
  • Tsunami waves retreat, just like regular ocean waves, and when they do the pull people and debris out with it.
  • Tsunami reached Hawaii and surged for over an hour. Wave strong enough to cause major damage, but tsunami warning system allowed people to evacuate.
  • As tsunami spreads, energy spreads out and so any particular location receives less energy. Circumference of a circle is 2 π r, so if the tsunami travels 2 times as far, it’s twice as powerful at any one given point on that new circle.
  • Aftershocks are less than the original earthquake, but some reach 6.2 since the initial Quake was 9.0.
  • Japan’s latitude is about equal to Northern California.
  • Formation of hydrogen gas (from water, also creates oxygen), lead to explosions that opened the containment buildings.
  • ‘Read to go’ in geologic time can be one second or 100 years.
  • Along the west coast, from Washington State to Northern California (near Eureka), the Cascadia fault is a ‘subduction fault’ like that in Japan.
  • The rest of California has the San Andreas Fault, which is a ‘strike-slip’ or ‘transverse’ fault; the magnitude of earthquakes on these types of faults is about 10 times less than subduction faults.
image showing tsunami travel times across the Pacific Ocean

Videos of the tsunami reaching North America

Richmond in the SF Bay
Santa Cruz
Crescent City
Morro Bay
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2/18 AP: Conservation of momentum book problems

animated gif showing Collision carts m1 greater than m2

Book reading/review

  • Review 6.2 Conservation of Momentum, pages 166-168
  • Read 6.3 Collisions, pages 168-175
    • Pay particular attention to the Problem-Solving Strategy method described on page 173.

Problems (pages 182-184)

Remember that only when a collision is described as elastic can you use conservation of kinetic energy.

6.2 Conservation of momentum

Problems 19, 20, 21

6.3 Collisions & Glancing collisions

Problems 25, 27, 28, 29, 31

animated gif showing Collision carts m1 greater than m2
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2/13 AP: p and K spreadsheet calculations

Photo showing two cars that collided front to side

Today you will finish your spreadsheet calculations.

Remember, momentum is a vector, so some of your velocities will be negative. Be sure to include these, and that they match the relative directions of your carts.

  • Start with one trial and:
    • Use formulas in the spreadsheet to calculate p, K, Δ , %, etc.
    • Once you have the trial with correct formulas, copy/paste those to all your other trials.
  • For Δ in p and K, we always use (final-initial).
  • For percent, we want to know the percent change, so use ( Δ / initial)
  • Add some colors to make it easier to read

Averaging explosions calculations

Problem

Since we want to calculate percent as compared to the initial, and the initial p and K are zero, we can’t divide by the initial. Instead, use the following formula (all momentum values are the final values, since the originals are all zero)“

Solution

Rationale

Numerator: If momentum is conserved, then pa + pb should equal zero (one value being negative), so the numerator in our traditional change/original calculation would be zero.

Denominator: We would want the denominator to represent some value we are comparing to, so let’s chose the average of the two momenta…but since one is positive and the other is negative, we need to take the absolute value of each before averaging them.

And finally…

If your group was not able to collect any data, please use the following spreadsheet and save a copy for your group. bit.ly/VHSmomentum

Here’s a video about momentum and kinetic energy in car crashes for your enjoyment:

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2/12 PotU: Momentum with Bill Nye

photo showing cue ball breaking a triangle of billard balls

Warm up

What has more momentum? A 2,000 kg car moving 10 m/s or a 1,500 kg car moving at 15 m/s?

Show the math you used in your warmup sheet.

I should be back tomorrow, so one more day of video. Please complete the worksheet as you watch the movie. You may ask your sub to pause the video when you need time to complete a line.

When you are done with the video, take any extra time to complete yesterday’s work. Turn in today’s video notes sheet as well as yesterday’s work before you leave.

Today’s video

If the video below isn’t Bill Nye SO2E17 Momentum, please reload this page to get the correct video.

https://youtu.be/X-czMvI65dY

Video questions handout

File Name: Bill-Nye-Momentum-Video-Questions-Trampleasure.pdf

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2/12 AP: Final momentum lab day

Screenshot of a spreadsheet

OK, unless I get hit by a truck, I will be back on Thursday.

Today, please work together to help all students complete their data collection and analysis Data analysis should include:

  • Description of each type of collision/explosion you created.
  • A list of the percent momentum and percent kinetic energy lost during each event.
    • Hint: Once you get your data entered into your spreadsheet, you should be able to calculate momentum and kinetic energy from the same cells for each event.
    • This is where consistency in your layout makes formula (equation) writing easy. Once you write the formula, just copy/paste to the needed cells.
  • Calculate the average momentum and kinetic energy lost for all your events.

Remember to submit your spreadsheets below. I’m still missing a few.

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2/11 AP: More on momentum

'Gritty people train at the edge of their comfort zone.'

My lengthy illness (severe sore throat, doc says it’s not coronavirus, but I did get tested for strep today) has presented an opportunity that I have always wanted to do, but never had the nerve to go through with:

Set a class to work on a topic and let them work it out with each other until they have it right, with no instruction from me (well, I have provided direct instruction last Monday and Tuesday, as well as some online videos and other tips).

I see you get down to work on whiteboards to solve problems from the book, but when you get your hands on equipment, many of you get frustrated when it gets hard.

Today’s the day to put all your brains together!

  • If your group has a lot done, collaborate with other groups to help them along.
  • Ask yourself what it is you are trying to measure, then decide how the equipment will get you that measurement.
  • Don’t worry about making a mistake; you may have to repeat yourself, but you can’t really break the equipment.

In the end, if you can work your way through this somewhat complex experiment, the ‘grit’ and collaborative skills you develop will be much more valuable than any physics you learn in here.

Don’t give up! You are all intelligent people who can figure it out.

You’ve probably heard about grit and perseverance, but here’s a short video that you might want to watch for more info:

“Gritty people train at the edge of their comfort zone.”

Here’s a video to show you two different ways to think about momentum, using Newton’s laws and Galilean relativity.

Here’s one telling you all about the units and equation for momentum.