Year 2018

MacGyver Season 1 Episode 2 Hacks

rhettallain 1 Comment

Now I’m excited.  This is an episode that I fully looked at before they started working on it.  Actually, it’s sort of funny.  I remember getting this script and I remember reading it.  I was on my way to give a workshop in South Africa and I had a 9 hour lay over in Paris.  I sat in a lounge chair and read this script.

Oh wait.  I even have a picture of where I was sitting.

Ok.  That has nothing to do with MacGyver or science – it’s just one of those things that comes to my mind.  I don’t know why.  Now for some science.

Episode 102 Metal Saw

Siphoning Gas

(Plausible, fluids, pressure)

A siphon is actually pretty cool.  The basic idea is that water (and most fluids) don’t really compress that much.  If you get a fluid in a tube and the fluid moves down – it would leave an empty space after it moves.  This empty space would have a region of lower pressure.  That means the far end of the tube will have a region of higher pressure due to the atmosphere.  This higher pressure pushes the fluid.

But here’s the trick.  You can get this siphon flowing by itself – but there can be no air in the tube AND the end point must be lower than the starting point.

Gasoline Draino and Fertilizer

(Plausible, chemistry, explosive)

Ok, let me get this out of the way.  The general rule for bombs is the following: any two or three chemicals mixed together can potentially explode.  The details don’t really matter too much.

Why? Well, first – bombs are dangerous and no one wants to encourage bomb making. Second, you don’t want to train people how to make real bombs.

Ignite Alcohol with Cigar

(Plausible, fire, burning)

Really, there are two questions here.  First, can you light alcohol on fire?  The answer to this one is – yes.  Often, the idea is that alcohol over 100 proof will burn – but that’s not always true. The important thing to realize is that it’s actually the vapors that ignite – not the liquid.

Now for the second part. Can you light it with a cigar?  Probably.  You really want an open flame – not a smoldering bit of tobacco.  However, if you suck in air – you can probably get it hot enough to ignite.  It’s not a sure thing though.

Dropping a rock down a shaft

(Real, physics, acceleration)

So, a rock drops down a shaft.  By measuring the fall time, you can determine the height.  I won’t go into all the physics details – but here is a post I wrote for something else.

Arc Welder from a Car Battery 

(Plausible, electricity)

Yes, you can use car batteries to make an arc welder – but a normal car battery is only 12 volts.  It looks like you would need a few more to get up to arc welding voltage.

But wait! Can you cut instead of weld?  Yes apparently.

Using a Camera to Make Infrared Night Vision Goggles

(Real, light, vision, infrared)

How can you see in the dark?  Answer: you can’t.  Humans need visible light to reflect off objects in order to see them.  No light means no seeing.

However, you can make a type of night vision goggles using infrared.  Infrared is just like visible light – but with a slightly longer wavelength.  Human eyes can’t see it.  But wait! Some cameras can indeed see infrared – and that’s where this hack comes from.

If you take some infrared lights – lights that only produce IR then they can shine on things and humans can’t see it.  That’s where the camera comes into play.  So, it goes like this:

  • Infrared lights (like from a TV remote or a security camera).
  • Camera to pick up reflected IR.
  • Video screen so that a human can see it.

Note: there was lots of back and forth getting this thing to work in the episode – but eventually we got something good.

Oh, there is a difference between NEAR Infrared and FAR Infrared.  Near IR is stuff that is almost the same wavelength as visible light – that’s what some cameras can detect it.  FAR infrared is stuff that we associate with thermal radiation – I will talk about this later.

Now for a video.

Sunlight and Mirrors to Ignite Ammo

(plausible, light)

Yes, the sunlight gets hot.  If you can collect enough and focus it – it will get hot enough to burn stuff.

Razor Wire Caltrops

(plausible, physical)

MacGyver makes some caltrops out of wire – straight forward.

 

List of Teaching and Learning Posts

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Here is a collection of post for students and faculty – all about learning to help with the start of the semester.

List of Tweet Threads

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https://platform.twitter.com/widgets.js

https://platform.twitter.com/widgets.js

https://platform.twitter.com/widgets.js

https://platform.twitter.com/widgets.js

https://platform.twitter.com/widgets.js

https://platform.twitter.com/widgets.js

https://platform.twitter.com/widgets.js

https://platform.twitter.com/widgets.js

The Physics of Scale

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Alternative title: “Big things are not small things”.

Here are some of my posts on the physics of scale.

MacGyver Season 1 Episode 1 Hacks

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Hello and welcome.  I should have started this a long time ago, but it’s never too late.  In this series, I am going to go through each episode of MacGyver (the reboot) and describe all of the science in the “Mac Hacks”.

Oh, I guess I should mention that I am the Technical Consultant for the MacGyver show – but maybe you already knew that.

I will also give a score for each hack.  Here is the grading scale.

  • Real. This is a real hack that would probably work.
  • Very plausible. This is based on real science, but might not work – it might require some luck to get it to work.
  • Plausible. Also based on real science, but it probably wouldn’t work as shown.
  • Iffy. Yeah, this probably wouldn’t work in real life and it might not even be based on real science.

Of course I will start with Season 1 Episode 1: The Rising. Note: I didn’t really work on this episode.

1) Finding Fingerprints.

(Very plausible, forensics, biology)

MacGyver uses tailpipe soot to sprinkle on a glass to find fingerprints.  He then uses tape to capture the print. I don’t really have much to say about this hack

2) Electromagnet.

(Iffy, physics, electromagnet, radio waves)

Getting the battery from a stud finder and stripping a wire and coiling around iron to make an electromagnet .  He then uses this to interfere with a radio.

Now for an explanation.  Ok, electromagnets are real.  An electric current does indeed make a magnetic field.  You can make a stronger magnetic field by forming a wire into multiple loops.  One quick note – you can’t use bare copper wire.  The wire has to have insulation around it – like rubber or enamel (a thin coating in magnet wire – used for motors).  If you add a ferromagnetic core (like iron) inside the loop, the magnetic domains in the core will line up with the magnetic field due to the loop and create a stronger magnetic field.

What about jamming a radio?  Radios send signals (and receive) using electromagnetic waves.  These are oscillations in both electric and magnetic fields (way more complicated than just one sentence – but that’s good for now).  So, can a magnetic field interfere with EM waves?  Not really.  What you COULD do is make an oscillating magnetic field.  This would in turn create an oscillating electric field and its own EM wave.  If the frequency of this EM wave is the same as the radio – boom – you have interference.

There are ways of making an oscillating magnetic field – but I will leave this for now.

3) Tricking a hand scanner.

(iffy, forensics, biology)

Put dust on a hand scanner and then blow off the excess.  The remaining dust sticks to residual oils.  Mac then covers over with his shirt.

This hack is fine for a show, but if these hand scanners were that easy to fool – wouldn’t everyone be doing it?

4) Paperclip picking handcuffs.

(plausible, physical hack)

I assume you can pick a lock with a paperclip.  Nothing more to say about this.

5) Smoke bomb.

(plausible, explosive, chemistry)

Mixing tinfoil, muriatic acid and ammonia to make smoke – yes, this makes lots of smoke.  Putting it in a closed bottle would be a bad idea though – it would probably create a small explosion when the pressure inside the bottle got too high.

6) DIY Bola.

(plausible, physical hack)

Mac builds a bola from a soda can filled with asphalt, and cut in half.  The two halves are closed up and tied together.  Nothing super special about this – but I am a big fan of these types of hacks where he actually builds some physical thingy.  It feels like the fundamental essence of MacGyverisms.

7) Disable aircraft landing gear.

(plausible, physical hack)

MacGyver uses his swiss army knife (SAK) to disable the retracting landing gear of a plane.  This seems very plausible.

8) Hot wiring a circuit.

(plausible, circuit)

Mac does some type of hot wiring – not sure what’s going on here.

9) Disable a bomb.

(very plausible, circuit)

I mean – MacGyver was a bomb guy in the army.  I’m sure he could figure out some way to disable this bomb.

Update on Python Physics Curriculum

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So here is the deal.  I had this idea.  The plan was to include numerical calculations into the intro physics curriculum by writing a sort of online textbook.  Or maybe just redo my Just Enough Physics ebook to include more numerical calculations.  Anyway, this is what I came up with. It’s written with trinket.io – an online implementation of python that pretty much rocks.

Here is my curriculum (it’s incomplete – but totally free).

Introductory Physics with Python

Here are some of my own thoughts on this curriculum (including using trinket.io):

  • It’s free and online.  That’s mostly good – but I don’t know if online is the best format for physics.
  • There is one thing about trinket.io that makes this rock.  There is python RIGHT IN THE PAGE.  Readers can view and run code – no logging in, no saving, nothing.  Just edit and run.  No barriers.
  • It has the same idea as Just Enough Physics in that it goes over the basic stuff – but doesn’t overload the student with tons of different ideas (no fluid dynamics, waves, buoyancy, sound…).  It’s not that those are bad topics, it’s just too much.  Too much.
  • Homework.  Students want homework questions.  I sort of added those in – but students seem to want traditional homework questions.

Now for the part that needs work.  Well, all of it needs work – it’s not complete.  But I made an error – I figured I would finish this curriculum as I was using it to teach the summer session of physics, but the pressure was too much.  In the end, I think I made it too much like the traditional format of a textbook (with the traditional order of topics).  Really, I started along the best path – but went off the rails when I wanted to do a problem that involved new physics.  So, I just added that new stuff in there.

I need to rethink just what I want to cover – and here is my new plan.

  • Kinematics in 1-D and 2-D. I like starting with kinematics because students can model motion and this works great with numerical calculations.  The one problem is that you have to use acceleration instead of change in momentum – and this messes up with my momentum principle.  Actually, maybe I will just do 1-D motion so that I don’t need vectors.
  • Forces. I don’t really want to focus on forces and equilibrium, but the students need this to do more stuff.  In this, I need to do the following.
    • Vectors.  Boom – need vectors.
    • Special forces: gravity, real gravity, maybe Coulomb force.
    • What about friction, and forces of constraint (like the normal force)?  Here you can see how it gets out of hand.  Friction is super crazy if you think about it – so are normal forces.
    • What if I just did simple forces – like pushing with your hand or rockets?
  • Momentum Principle.  Here I need to make a connection between forces and motion.  Since I used acceleration before, I need to make a connection between the momentum principle and \vec{F}_\text{net} = m\vec{a}.  Honestly, I hate calling this Newton’s Second Law – it seems wrong.
    • But what about circular acceleration?  How do you deal with that?  I don’t know.  Maybe just avoid it for now.
  • Work Energy Principle. I think this is mostly ok – except I need to introduce the spring force and spring potential energy.
  • Angular Momentum Principle.  My initial idea was to cover “Three Big Ideas” – momentum principle, work-energy, angular momentum principle.  However, there is SO MUCH baggage associated with angular momentum principle.  Much of this stuff is just beyond intro-level students.

I think I have a new plan.

  • Start with kinematics in 1-D.
  • Forces – but simple stuff.  No friction.  No normal forces.  All the examples will be in space or something.
  • Momentum Principle and acceleration. Again, normal stuff.  No forces of constraint.  Mostly space stuff because that will be fun.  Projectile motion stuff too.
  • Work-Energy Principle.  Springs, gravity, dropping objects.  Orbits.
  • Special cases.  Instead of Angular Momentum, I’m going to go over forces of constraint, friction, normal forces, circular acceleration.

The end.  Oh, I need to make sure there are plenty of exercises for students.  Rewrites coming.

Thinking about labs

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I need to redo all my physics labs.  They are terrible.  I want to make them even MORE about model building.

With that in mind, I saw this:

 

One sentence labs.  Leave the procedure up to the students.  I think I will need some type of turn in sheet for these labs though.  What about informal lab reports?

Picking up trash

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There was this very nice lady in our neighborhood.  She would take it upon herself to pick up trash along the main road next to the subdivision.  Super nice lady.

Well, she moved.  She moved to live with her kids (she was older).  So, as a way of respecting her service I went on amazon and ordered a pair of those stick grabber things.  Now it would be my duty to keep that road clean.

The first time I picked up trash, my oldest daughter volunteered to go with me.  There was a BUNCH of stuff.  Crazy stuff.  I think we filled up three trash bags for about a mile of road.

Cigarette butts are all over the place.  Styrofoam cups, beer bottles, vodka bottles, and other various things (some of which I shouldn’t mention).  It was hot and buggy.

But in the end, we finished.  The road looked better.  The next day, I saw a cup. WHAT THE HECK???? I just cleaned up (we just cleaned up) and there already was a stupid cup on the side of the road.  Who does this?

So now, I go about once a week.  I pick up trash.  It’s hot – but I really like it.  It’s like one of those chores that you oddly enjoy.  It’s like vacuuming the floor and it looks all neat afterwards.  Or mowing the lawn, or cleaning the bathroom.  I sort of like these jobs that clearly make a difference.  On top of that, picking up trash is about more than just me – it’s a sort of community service.

Oh, and I get some exercise too.  To summarize: don’t pick up trash on the road – it becomes addicting.

The worst high school physics question EVER

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Here is a multiple choice question from an online high school physics question.  It’s bad, but it’s probably not actually the worst ever.

It goes something like this:

You have three objects that start at the same temperature.  Which one cools off the fastest?

  1. A dry bean
  2. Toast
  3. Water

What is your answer and why is this bad?

I’ll be honest, I answered this question incorrectly – well, I should say that my answer didn’t agree with the key.  Let’s go over the options.

Water

I’m starting with water because this is the answer I chose.  Why would water cool off the fastest?  My assumption was that the water would evaporate and cool off the liquid more than the other two objects.

Of course the evaporative cool depends on several things:

  • The water temperature
  • The air temperature and humdity
  • The volume of water
  • The surface area of water.

If I take some water and pour it into a very shallow pan with a large surface area, this stuff is going to cool off quick.  Note: here is an older post about evaporative cooling.

This answer was wrong.

Toast

This was my second answer.  What is special about toast and why would they choose it?  In my mind, toast is special because it has lots of holes.  Lots of holes means that it has a large surface area to volume ratio.

Since things radiate thermal energy through the surface area, things with high surface area to volume ratios cool off faster.  This is why small objects cool off faster than large objects.  This is also why the moon’s core is cooler than the Earth’s core (the moon is smaller).

Oh, this is also how a heat sink works.  Large surface area to volume ratio.

This answer was wrong.

Dry Bean

A dry bean could cool off the fastest because it is small (high surface area to volume ratio) and it is low density.  I assume if it has a low density it has a low specific heat capacity.  This means that with a low specific heat capacity, the dry bean has a small amount of thermal energy even though it has the same temperature as the water and the toast.

This is essentially the same reason that you can put pizza on aluminum foil in the oven.  Once it is hot, you can touch the aluminum foil, but not the pizza.  Although they are at the same temperature, the aluminum foil has less thermal energy to burn you (because of the low mass).

This was the correct answer (according to the people that wrote this dumb question).

Writing questions isn’t so simple

I think what the author really wanted to ask was “which has the lowest thermal energy?”  But even then, you have to take mass and specific heat capacity into consideration.

It’s really just a super bad question.  Super bad.  Oh, but it’s probably not the worst one.  I saw some others that were just as bad if not worse, but I have blocked them from my memory.

Reflections on Student Video Assessments

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After the summer session of physics (algebra-based), I have the following comments.

  • It seems like every other video has a problem with vector notation.  Students often set a vector equal to a scalar.  Frustrating.
  • Students seem to confuse two standards: The Momentum Principle and Collisions.  I have students submit videos for the momentum principle that are just a collision.  The key point is that the momentum principle deals with force, time and change in momentum.  I guess this is my fault. I offered suggested homework problems from a textbook and it covered momentum and collisions in the same chapter.  I guess they thought they were the same thing.
  • Students are not very skilled at picking problems to solve.  They like the lowest level of something like “mass is 2 and velocity is 3, what is the momentum?”. I tried to help them, but it didn’t seem to work.  I showed a bunch of questions in class and had them “rate” them then discuss what makes a good problem. (I think I wrote about that here on my blog).
  • I’m still not happy with the “student review”.  I want students to watch other student videos – but I don’t know how to implement that.
  • Students like to procrastinate.  I’m getting a bunch of redos on the last day of submissions.  That sucks to grade.
  • I hate vertical videos – but I hate videos that are recorded sideways even more.  I stopped accepting the sideways videos since they can fix it and send it back to me.
  • I try to give meaningful feedback in my responses – but sometimes I just give a grade (score out of 5 points).
  • I’m trying to give higher scores.  If they do well on the in-class assignment and submit multiple videos that aren’t wrong, I typically will at least give a 4/5.