# MacGyver Season 1 Episode 17 Science Notes: Ruler

Propane tank flame thrower

Take a propane tank and bicycle tube. Cut the bike tire to make it a hose and connect it to the propane tank. Use a road flare to light the gas—boom. There is your flame thrower.

Oh but wait. It’s just a dream. Bozer’s dream. The flame thrower wasn’t real anyway.

Listen in on a landline phone

Who uses a landline now anyway? Oh well. They want to use a landline then it’s possible to listen in. Actually, this isn’t even that difficult. Check it out.

Here is another version.

You just need a capacitor and maybe an inductor. You could grab these from a radio or something like that.

But wait. I made a mistake. While going over this hack, I said something like this:

“Yeah, this is pretty easy. Just get the capacitor and earpiece (or radio) and then tie it into the wiring box”

Here’s what that looks like.

I just want to point out this small mistake (that you would never notice) just in case you saw it. You don’t actually “tie” the lines—that’s just a term we use in circuits to mean “connect”.

Bomb radius calculation

There’s a bomb in the truck. Where should you park it so that no one gets hurt? Yeah, this is a tough calculation. However, tough has never stopped MacGyver before and it won’t stop him now.

Here is my rough calculation and explaination.

Bombs are complicated. But usually it is the pressure produced by the explosion that will get you. We can come up with some pretty useful models to calculate their impact. First, there is the Hopkinson-Cranz Scaling Law (this is a real thing). With this law, the acceptable distance can be calculated based on the explosive weight.

$\mathrm{Range} = (z)(\mathrm{weight})^(1/3)$

In this expression z is a factor that depends on the type of distance with 14.8 being the distance factor for a public traffic route. That means that 2 kilograms would need 18.6 meters (60 feet).

Infrared face jammer

OK, it doesn’t actually jam your face. That would be weird. MacGyver wants to prevent the security cameras from recognizing their faces. So he takes some infrared TV removes and pulls out the IR LED lights. Normally these flash on and off so that the sensor on the TV can “see them” but humans can’t.

He mounts these IR LED lights on some sun glasses with a battery to power them. When a security camera sees the face, it just gets blinded by the IR light since many video cameras can also detect IR.

If your phone camera doesn’t have an IR filter (most now do) then you can actually see the light flashing on a TV remote by pointing it at your phone.

Oh, so this could really work. It just depends on the type of video cameras. Some people even put stuff like this on their car license plate so that police cameras can’t see them.

Car jacking

How do you open a locked car door? One way is to jam a wedge into the door. This will pull the door out just a little (by bending it) so that you can get a stick in there. The stick then can be used to push the “lock” button.

In this case, MacGyver uses something for the wedge—maybe a shoe horn or a door stop. Then a monopod is extended to click the lock button.

DIY soldering iron

You might have missed this one. But as MacGyver is building his stuff for the last mission, he needs a soldering iron. He takes the heating element out of a hair dryer and connects it to some stuff. That works.

Fake noses

Need a disguise? How about DIY latex to make a nose? Yes, this seems plausible. Here’s how to do it.

DIY keypad cracker

MacGyver makes a quick circuit board that can crack a keypad by using a brute force method that goes through all the combinations. This is from a different episode, but it’s the same idea.

If you want to play with one yourself, here is an online version of the code.

DIY police radio

Well, it’s just a radio. MacGyver needs a speaker and a transmitter. Really, a radio transmitter is essentially the same thing as a radio receiver—OK, not really but sort of.

Instead of going over the way MacGyver did it, how about a real actual radio you could build yourself? Here is a spark gap transmitter from simple parts (and awesome).

Here is a more detailed explanation of the spark gap transmitter from one of my WIRED posts.

# MacGyver Season 1 Episode 16 Science Notes: Hook

Quicksand

Yes, it’s true. You don’t really sink all the way down in quicksand—that’s because the density of the stuff is greater than the density of water. Essentially, you float.

Here is a nice video on quicksand.

Pool shot.

I. Love. This. So, MacGyver is there trying to score a nice shot in pool (the game, not the pool). He starts thinking about all the physics to get the perfect shot—one with some curve. Here is what goes through his mind.

That’s pretty awesome, right? Let’s go over some of the key equations.

First, why does the ball turn? If you want to turn, you have to have a sideways force. In this case, the sideways force is a frictional force on the ball as it spins and slides on the table.

Once you know the frictional force, you can use this to find the new vector velocity after some short time. This is basically the numerical version of the definition of acceleration. Here’s that equation.

$\vec{v}_3= \vec{v}_2+\frac{\vec{F}_f}{m}\Delta t$

Oh, vectors. Look at the vector notation. Winning.

Next there is the changing angular speed of the ball. Since the ball is spinning with a frictional force, the ball would slow down. We describe the change in angular motion by using the angular momentum principle. This states:

$\vec{\tau} = \frac{\Delta \vec{L}}{\Delta t}$

Where L is the angular momentum vector. For a rigid object, the angular momentum is the product of the moment of inertia and the angular velocity (for most cases).

$\vec{L}=I\vec{\omega}$

Where I is the moment of inertia (or as I like to call it, the rotational mass) for a sphere.

$I = \frac{2}{5}MR^2$

That’s pretty much all the equations you see.

Of course the amazing part is that humans can make these very complicated shots WITHOUT doing the calculations. I don’t know how that works.

Zip-tie nunchucks.

Two broken pieces of a pool stick and a towel. Boom. Nunchuck. But this is all I can think of.

Magnet phone tracker

How do you track a fleeing truck? You stick your smart phone on the bottom using a magnet. Oh, this works so well that Spider-Man used this same trick the following year in Spider-Man: Homecoming when he left his phone in the Vulture’s car.

There is a small problem with those car magnets. They are like refrigerator magnets in that they have weird magnetic domains. Actually, you should try this experiment.

• Grab a fridge magnet.
• Flip it around and put it on the fridge.
• Oh, it doesn’t work!

The magnetic domains in these flat magnets are such that they stick on one side but not the other. That makes it tough to use for a magnetic phone tracker.

A better method would be to run a wire (or zip tie) through the magnet and around the phone. Like this.

Stab pepper spray with a knife

Yes, if you poke a hole in a can of pepper spray it will get pepper spray all over the place.

Circuit board knife

MacGyver uses a broken circuit board to cut through zip ties. Zip ties aren’t that strong anyway—it seems very plausible that you could sharpen a circuit board to cut through one of these things.

Control a car remotely

Is it possible to control a car with a computer? Sadly, this is real.

Moonshine spray

MacGyver sprays 155 proof moonshine and threatens to light it. Yes, 155 proof can catch on fire.

# Electric Field due to a Uniformly Charged Ring

Hold on to your pants. Let’s do this.

Suppose I have an electrically charged ring. The radius of this ring is R and the total charge is Q. The axis of the ring is on the x-axis. What is the value of the electric field along this x-axis?

Analytical Calculation

You can’t directly find the electric field due to a charge distribution like this. Instead, you have to break the object into a bunch of tiny pieces and use the superposition principle. The super position principle says that the total electric field at some point is the vector sum of the electric field due to individual point charges.

Of course the electric field due to a single point change can be found as:

$\vec{E}=\frac{1}{4\pi \epsilon_0} \frac{q\hat{r}}{r^2}$

So, if I break this ring into a bunch of tiny points I can find the electric field due to each of these points and add them up. Yes, the smaller the points the better the answer. In fact, if I take the limit in which the point size goes to zero I will turn this into an integral. Calculus for the win (CFTW).

Let’s take a look at one of these pieces on the ring of charge. Here is a view of the ring from the side.

I can find the little bit of electric field from this little bit of charge at the top of the ring. This electric field would be:

$d\vec{E}=\frac{1}{4\pi\epsilon_0}\frac{dq\hat{r}}{r^2}$

Of course the direction of r and thus the electric field will change directions as you go around this ring and add up tiny electric fields. But WAIT! We can cheat. OK, it’s not cheating–it’s just being smart. What if you also consider the tiny piece of charge at the bottom of the ring? This would also make a tiny electric field at this same location. It would have the same magnitude as the electric from the top piece since it’s the same charge and distance. However, the y-components of these two electric fields would cancel and leave only an x-component of the field.

In fact, for every tiny piece on the ring there is a corresponding piece on the opposite side of the ring. The only surviving components of electric field will be in the x-direction. So that’s all we need to calculate.

Looking at the diagram above, I can find the x-component of this tiny electric field by using the angle θ (which I don’t explicitly know). However, I can still write down this new x-component of the tiny electric field.

$dE_x = \frac{1}{4 \pi \epsilon_0} \frac{dq}{r^2}\cos\theta$

Yes, this is no longer a vector. It’s the x-component of the electric field such that it’s just a scalar. But there’s still a problem. I want to add up (thus integrate) all these tiny electric fields due to the tiny charges. However, I have these two variables that I don’t like. There is θ and r. I need to replace those.

For the r, it’s clear that I can use R and x and the pythagorean triangle to get:

$r^2=R^2+x^2$

I can also replace the θ by again using the right triangle to write:

$\cos \theta = \frac{x}{\sqrt{R^2+x^2}}$

Updating the tiny x-electric field:

$dE_x = \frac{1}{4 \pi \epsilon_0}\frac{dq}{R^2+x^2}\frac{x}{\sqrt{R^2+x^2}}$

This simplifies to:

$dE_x = \frac{1}{4 \pi \epsilon_0}\frac{xdq}{(R^2+x^2)^{3/2}}$

Now we need to get a better integration variable—we can’t integrate over dq. Or can we? Yes, we can. Take a look at the equation above. As you move around the circle, which of those variables change? The answer: none of them.

As I integrate over dq, I just get the sum of the dq’s—which would be Q. Boom. That’s it. Here is my final expression for the x-component of the electric field along the x-axis of this ring.

$E_x = \frac{1}{4 \pi \epsilon_0}\frac{xQ}{(R^2+x^2)^{3/2}}$

Now for a couple of checks on this result. I will let you make sure these are ok.

• Does this expression have the correct units for electric field?
• What about the limit that x>>R? Does this expression look like the field due to a point charge?
• What is the electric field in the center of the ring?

One last thing to think about. What if you want to find the electric field at some location that is NOT on the x-axis? Then the above derivation wouldn’t work. Too bad.

Numerical Calculation

Let’s do this again. However, this time I am going to create a numerical calculation instead of an analytical calculation. What’s the difference?

• The analytical calculation takes the sum of charge pieces in the limit as the size of the pieces goes to zero.
• The numerical calculation uses numerical values for a finite number of pieces to calculate the electric field.

That’s really the only difference.

OK, let’s just get into this. I’m going to give you a link to the code and then I will go over every single important part of it. Honestly, you aren’t going to understand this code until you play with it and probably break it.

Here is the code on trinket.io. Sorry—I can’t embed the code in this wordpress blog (I wish I could).

This is where I start.

k=9e9
Q=10e-9
R=0.01


I like to start with some constants and stuff. Here I am using k for the constant. I also had to pick a value for the total charge and the radius of the ring. Remember, you can’t do a numerical calculation without numbers.

Now let’s make the ring.

cring=ring(pos=vector(0,0,0),axis=vector(1,0,0), radius=R,thickness=R/10, color=color.yellow)

Some notes.

• This isn’t really needed for the calculation—but it allows us to make a visualization of the thingy.
• “ring” is a built in object in VPython (glowscript).
• The important attributes of this object are the position (pos), the axis—which is a vector in the direction of the axis of the ring. Radius and thickness and color should make sense.

For the next part, I need to break this ring into pieces. If I use N pieces, then I can find the location of each of the tiny charges by using an angle to indicate the location. I also need to find the charge on each tiny piece. Here is the important code.

N=20
theta=0
dtheta=2*pi/N
dq=Q/N


The “dtheta” is the angular shift between one piece and the next. It’s like a clock. It’s a clock that only ticks N times and doesn’t really tell time. But each “tick” is another tiny charge. Maybe that’s a terrible analogy.

But how do we deal with all these tiny charges? What if N is equal to 50? I don’t want to make 50 variables for the 50 charges. I’m too lazy. So instead, I am going to make a list. Lists in python are super awesome.

I won’t go into all the details of lists (maybe I will make tutorial later), instead I will just show the code and explain it. Here’s where I make the tiny charge pieces.

points=[]

while theta<2*pi:
points=points+[sphere(pos=R*vector(0,cos(theta),sin(theta)),radius=R/8)]
theta=theta+dtheta


Some notes.

• First, I made an empty list called “points”.
• Next I went through all the angular positions around the ring. That’s what the while loop does.
• Now I create a sphere at that angular position and add it to the points list.
• Update theta and repeat.
• In the end I have a list of points—the first one at points[0].

Next part—make the observation location. This is the spot at which I will calculate the electric field.

obs=sphere(pos=vector(.03,0.03,0), radius=R/10)
E=vector(0,0,0)


The “E” is the base electric field, it starts at the zero vector.

Now for the physics.

for p in points:
r=obs.pos-p.pos
dE=k*dq*norm(r)/mag(r)**2
E=E+dE

print("E = ",E," N/C")


Here you can see the full power of a list. Once I make the list of tiny charges, it is very simple to go through the list one tiny charge at a time—using the “for loop”.

Essentially, this loop does the following:

• Take a tiny charge piece.
• Find the vector from this piece to the observation location
• Find the tiny component of the electric field using the equation for a point charge.
• Add this tiny electric field to the total electric field and then move on to the next piece.

Boom. That’s it. Print that sucker out. Maybe you should compare this electric field to the analytical solution. Oh wait. There’s a bunch of homework questions. Actually, I was going to do some of these but this post is already longer than I anticipated.

Homework

• Pick a value of N = 10 and an observation location of x = 0.1 meters. How well does the analytical and numerical calculations agree? What if you change to N = 50? What about N = 100?
• Create a graph that shows the magnitude of the electric field as a function of x (along the ring axis). In this graph include the analytical solution and plots for N = 10, 30, 50, 100.

Actually, I wanted to make that last graph. It would be great.

Oh wait! I forgot about the most important thing. What if I want to calculate the electric field at a location that is NOT on the x-axis? Analytically, this is pretty much impossible. But it’s pretty easy with a numerical calculation. Here’s what that would look like.

Oh, if you like videos—here is the video version of this post.

# MacGyver Season 1 Episode 15 Science Notes: Magnifying Glass

It’s too late to change now—but I wish I had planned better for my titles for these science notes. I just don’t like the way it looks. Oh well. On to the science.

Jumping out of window with a TV cable

MacGyver yanks a TV cable from the wall and ties it around him. Then boom—he’s out of the second story window to catch a bad guy. As he falls, the cable gets pulled from the wall and sort of prevents him from a full force impact with the ground.

Electrostatic dust print lifter

Electrostatic dust print lifters are indeed real. Here is an example of a real one.

The basic idea is to take a conducting sheet and lay it on top of the area where you want to find a print (finger print or shoe print). When a large electric field is applied, the dust literally gets lifted and stuck to the conducting sheet. Boom. There is your print. Oh, you need about 800 volts to get a high enough electric field (according to one paper that is no longer online for some reason).

For the MacGyver version, he uses some mylar for the sheet. In order to create the large electric field, he can use the charging capacitor for the flash in a disposable camera. That might not get up to 800 volts, but it’s a good start. Yes, it’s also true that you can get fairly high voltages just by rubbing two different materials together—as long as the air is dry. This is exactly what happens when you rub your feet across a carpeted floor and then shock the bejeezus out of someone. Same idea.

One more thing. The official version of the electrostatic dust print lifter is pretty expensive. But someone made one for just 50 dollars using a stun gun. Here is the hackaday.com link, but it looks like the original post has link rotted.

Just to show you some more electrostatic stuff—here are some demos that you could try.

Open an envelope with steam from a radiator

Yup, this works.

Wifi wall detector

OK, it doesn’t detect walls. Instead, the wifi can find empty spaces behind walls. MacGyver takes a wifi router with a partially parabolic dish (using aluminum foil) over the antenna. He then connects the output to a speaker (for a cool effect).

Yes, wifi is essentially a radio wave (it is a radio wave). Radio waves mostly pass through walls—but you have wifi in your house and you know that sometimes you don’t get a great signal. This shows that wifi is at least partially blocked by walls. The wifi can also reflect off stuff.

It is this reflected wifi that MacGyver uses to find the hidden room. When there is nothing on the back side of a wall, you don’t get a good reflected signal and that changes the sound of the connected speaker.

OK, this probably wouldn’t work—but it’s still based on this idea that wifi can interact with walls in different ways. Anyway, MIT has created a tool to use wifi to see through walls. Note, this show came out before that. I’m not saying MIT based that wifi thing on this episodes. I’m just sayin.

Movie film roll for distracting fire

MacGyver takes one of those movie film rolls. Adds some stuff and then lights it on fire. When he rolls it down to the front of the movie theater—boom. Distracting explosion. Yeah, lots of stuff burns. No problem here.

# Modeling a falling slinky

I already posted some stuff about the MythBusters Jr. slinky defying gravity thing—here are those notes.

But how do you make a model of a falling slinky? Remember, you don’t fully understand something until you model it.

Also, with a model you can quickly test different situations. What happens if you put a car on one end of the slinky (or massive spring). What kind of spring constant do you need? What if the two masses are different?

All of these questions can be investigated with a model.

Let’s get to it. Of course, I am building my model with python—because I like python (and so should you). Here is my code. This is what most of it looks like (sorry, I can’t embed here).

Here is a gif of the output.

Some notes:

• The balls wait a short time before dropping—just to make it dramatic.
• I have calculated the position of the bottom mass so that it starts in equilibrium. If you don’t do that, the bottom mass will just oscillate up and down and ruin the whole thing.
• I added two objects—a stick on the side and a free falling ball. That way you can see how the spring thingy falls.
• Oh, you should absolutely try changing things up and running the model.

Here is how the model works.

• There are two masses (the ball1 and ball2)—just ignore the other objects, they don’t matter.
• Once the top mass is let go, there are two forces on the two balls. The downward gravitational force and then the spring force. Whatever the spring force on the bottom ball is, the top ball has the opposite.
• The gravitational force is easy to calculate.
• For the spring force, you need to know the natural length of the spring and the distance between the masses. The spring force depends on the difference between the distance and the natural length—then just multiply by the spring constant. Yes, I often mess up the sign on this force so that the two objects get pushed away in a weird motion.
• After that, you are pretty much done. Use this force to update the momentum and then use the momentum to update the position.

Homework.

Here are some things for you to try.

• What if the top mass is 0.1 times the bottom mass? Does this still work?
• What if the bottom mass is 0.1 times the top mass?
• See if you can calculate and plot the vertical motion of the center of mass of the two ball system.
• What if the spring also has mass? There is a way to model this, but I’m going to make you think about it first.
• Suppose I want to do this with a 2000 kg car. What spring constant would I need? What natural length of a spring should I use?

# MacGyver Season 1 Episode 14 Science Notes: Fish Scaler

Isn’t it nice that I have written enough of these MacGyver science note posts that I no longer have to give some witty introductory comment? Oh, I guess that was an intro comment. OK—next time it’s just going to jump into the science.

Picture triangulation

MacGyver is trying to track down some dude. He finds a skyline picture that he drew and assumes the guy drew it from his apartment window (somewhere in Atlanta).

Oh wait! I think I can find out where this guy lives based on the drawing. True? Yes, this is true. If the guy drew a scale drawing, then yes—it’s entirely possible to find out where he drew it from. Oh, if he does an abstract drawing then all bets are off. Right?

There is a lot here, so let me go over two important ideas needed to backwards engineer this drawing.

First—angular size. You already know about angular size. The farther away something gets, the smaller it looks. If you like, you can make it so that someones head appears to be as big as your thumb. Yes, the human would have to be much farther away than your thumb (from your eye).

If the thumb covers up someone’s head, then the two objects would have the same angular size. How about a diagram to explain angular size? Suppose some object has a length of L and is a distance r away from an observer. It might look like this.

The blue circle is the observer and the red thing is the object. Yes, I drew it as an arc of a circle. If the object is far enough away, this is very good approximation. That means I can use the arc length equation. Remember that if you go all the way around a circle, then the total length is $2\pi r$. That means I get the following:

$L = r\theta$

Assuming the angle θ is in radians and not degrees. Oh, here is a more detailed explanation of the difference between radians and degrees. But in the end, if you know two of the things (angle, distance, size) you can find the third thing.

If MacGyver sees a building that he is familiar with, he knows the size of that building (or at least he could look it up). But he doesn’t know the distance or the angular size—bummer. If this was an actual photograph, it’s possible he could determine the angular size of the building based on the angular field of view for the camera. However, this is drawing, so the entire width of the picture could be just about anything.

Now for the next idea—triangulation. Suppose you know the angular position of two objects. From those angles, you can draw two lines at those angles. Where those two lines meet—that’s your location.

But you can see the problem, right? The triangulation depends on the angular size of the drawing and so does the distance to the objects. It looks like a dead end. But it’s not. Actually, you have enough information to math-it-out if you try (and boy did I try).

I’ll be honest. I worked on this problem for quite some time. Here is one of my earlier sketches for this calculation.

But yes, it does involve some trig.

Hot wire a car

Everyone wants to steal a car. Honestly, modern cars are fairly difficult to just take. There are four or three (depending on how you count) different classes of cars. Let me list them.

• Super old cars. These have a key that starts the car. That’s it. You can steal these—BUT YOU SHOULD NOT STEAL CARS.
• Just plain old cars. These are like super old cars, but they have a steering wheel lock. Sure, you can hot wire these—but you can’t turn the steering wheel.
• Modern cars. I think it’s cars after 1997. These cars have a chip in the key. No chip, no start. Well, you might be able to start it but the car’s computer won’t pump fuel or something like this.
• Even more modern. What about those cars with the key fob and you don’t even put the key in the car? You can’t really hot wire those either.

But check it out. This guy has a great video that goes over the different types of cars and how thieves would steal them (but don’t steal cars).

So, in this case MacGyver hot wires a car. It looks like an older model—so it’s at least plausible. What about the steering wheel lock? Maybe he just yanked on the steering wheel really hard and broke the steering wheel lock.

Cleaning bottle bolo

This is pretty straight forward. MacGyver uses a string to tie two bottles of cleaning solution together. He then swings these around and throws them at a baddies legs. The thing is a bolo. It wraps up his legs and he falls like an AT-AT on Hoth (but a lot faster).

Trip wire fan

MacGyver runs a fishing wire in a hallway and then back to the room. The wire then connects to the switch in an electrical fan. When someone steps on the fishing line, it connects the switch inside the fan and turns it on.

This should work.

Bump key

The bump key is a tool used to pick locks. The main goal in lock picking is to move lock pins up out of the lock cylinder so that you can turn the key. Here is a better explanation (I’m not really an expert here).

Light explosion

How do you make a distraction in a parking garage? One way might be to jam a charger for an electric car into a power box for the overhead lights. That’s what MacGyver did.

Would this work? It’s possible. Most car chargers run at 220-240 volts, but most overhead lights are fluorescent lights that expect 120 volts. If you double the voltage, then bad things can happen.

Basically, there is an electrical ballast inside the fluorescent light. This is a transformer that takes the 120 volts and ramps it up much higher (depending on the length of the tube) so that you can make light. If the voltage is too high, the ballast could go boom.

# MacGyver Season 3 Episode 14 Science Notes: Father + Bride + Betrayal

Hotel door break in with a coat hanger

MacGyver uses a series of coat hanger wires to build a device that opens a hotel door from the inside. It’s basically a long wire that goes under the door and pulls down on the handle from the inside. Here is a video of what that looks like.

Don’t break into other people’s hotel rooms. That’s illegal. You have been warned.

Oh, but that’s not the best part. MacGyver says this is really about torque. Yes, that’s true. You need to exert a torque on that inside handle to get it to turn.

Wait. The real best part is when Riley says “It means physics is awesome”. Yeah it does.

Thermite toothpaste

So the bad dude that is turning himself in has a special safe. If you try to break in—thermite melts the stuff inside. Yes. Thermite is real and thermite is awesome. In fact, here is an older video where we set off some thermite as a chemistry demo.

We need to do this again.

OK, but could you make thermite into a paste? You might be thinking “oh, if you put the thermite in toothpaste, it won’t get as much oxygen for the reaction.” Good idea—but surprise! Thermite has its own supply of oxygen. You can even get a thermite reaction to work underwater.

Really, the only issue with toothpaste is that you don’t want to get the thermite stuff (particles) too far apart so that they can still interact with nearby particles.

Spray can flame thrower with a bonus

Yes, we pretty much all know that if you get a spray can and shoot it into fire you get a mini flame thrower. Oh, I’ve never done this myself but I know a friend of a friend that did it that one time. I’m sure you’ve never tired this either.

But what about the bonus? If you get any type of fine powder, it also explodes (that’s the powdered sugar part that adds to the flame thrower). Yes, when particles are very small and very spread out—they can explode.

Here is an example from season 1.

Cyanide detection

It turns out that there is a fast method to test for cyanide poisoning (which can happen from certain fires—not just for spies).

Here is an article on how this works— https://phys.org/news/2015-03-cyanide-poisoning-seconds.html.

The basic idea is to get the cyanide the cyanide by mixing the blood with both an acid (muriatic acid and/or vinegar) and a base (like baking soda). Add this to a fluorescent agent like a detergent and then look at it with an ultraviolet light. If it glows—it’s cyanide. At least this is plausible.

Cyanide antidote

For the antidote, MacGyver is basically going to make sulfanegen—an experimental cyanide antidote. Yes, humans do indeed build up a sort of tolerance to cyanide since it’s a natural element in many fruits and stuff. Here is my half-plausible method.

• You need sulfur. You can get this from match heads. Yes, that’s true.
• Acid—cleaning supplies.
• Hydrogen peroxide
• Blood. Yes—that might be gross, but you do need that.
• Heat it up and filter it with a coffee filter.

Now, how do you get it to Riley? You could use an IV—but a nasal spray should work too. This is why they give some kids the flu vaccine with a nasal spray.

Don’t actually try to cure someone with this recipe.

Finding the real bad person with interference

MacGyver uses the interference sound from Riley’s radio when she is attacked to figure out that someone is the bad person. Basically, someone had a device that interfered with the radio.

If you had a mobile phone (we didn’t call them smart phones because they weren’t that smart back then) in 90s or early 2000s, then you know what happens when they get near a speaker.

It’s entirely plausible that a medical alert bracelet could do this. In fact, medical equipment often uses older technology because they don’t like to move to newer stuff until it’s been fully tested.

In fact, there could be some type of extra interference caused by the taser and the medical bracelet. That’s what MacGyver wants to reproduce and detect. All he needs to do is to reproduce the taser signal and create an audio output so that he can “test” different people and find the baddie.

# Analysis of a borked lab

It happens all the time. It even happens to you. There is a new lab you want to try out—or maybe you are just modifying a previous physics lab. You are trying to make things better. But when the class meets—things fall apart (sometimes literally).

Yes. This is what happened to me this week. And yes—it’s OK.

But let’s look at the lab and go over the problems so that I can make it even better for the future.

Finding the electric field due to a point charge

This is a lab for the algebra-based physics course. It’s always tough because many of the first things they cover in the lecture class don’t have lab activities with things you can measure. Oh sure—there is that electrically charged clear tape lab, but it will be a while before they get to circuits.

So, my idea was to have the students use python to calculate the electric field due to a point charge. This would give them a safe and friendly introduction to python so that we could use it later to get the electric field due to other things (line a dipole or a line charge). It would be great.

Here is the basic structure of the lab (based on this trinket.io stuff that I wrote – https://rhettallain_gmail_com.trinket.io/intro-to-electric-and-magnetic-fields#/introduction/vector-review

You can look at that stuff, but basically I give a workshop style presentation and have the students do the following:

• Review vectors. Add two vectors on paper (not with python).
• Find the displacement vector – given the vector for a point, find the vector from that point to another point (the vector r).
• Find the unit vector and the magnitude of a vector (using python).
• Next, find the electric field due to a point charge for the simple case with a charge at the origin and the observation point on the x-axis. Do this on paper.
• Now do the same calculation with python.
• Find the electric field at some location due to a charge not at the origin (in python).
• Use python (or whatever) to make a graph of the electric field as a function of distance for a point charge. Graph paper is fine. If they wanted to, they could do the calculations by hand (or use python).
• Finally, give a quick overview of the sphere() and arrow() object in glowscript.

So, that was the plan.

Lab problems

Here are the problems students had during this lab.

• Computer problems. Yes—whenever using computers, someone is going to have a problem. In this case, it was partly my fault. There was one computer that was broken and some other ones weren’t updated. Honestly, the best option is for students to bring their own.
• I can see that there are some students that just sort of “shut down” when they see computer code. They automatically assume it’s too complicated to grok.
• Students working in big groups. I hate having 4 students use one computer. That’s just lame.
• Too much lecture. The first time I did this, I spent too much time going over vectors with not enough breaks for students to practice. I partially fixed this for the second section of lab.
• Some students were just lost on vectors.
• Yes, the unit vector is a tough concept.
• I’ve learned this before—but I guess I need to relearn. The visualization (sphere and arrow) are just too much for many students. That’s why I moved it to the end in my second section.

So, that’s it. I am going to rewrite the lab stuff on trinket.io. I am also going to change my material for the dipole stuff that they are doing next week. Hopefully it goes well. Let’s just see.

# MacGyver Season 1 Episode 13 Science Notes: Large Blade

Tarp restraint

This is sort of like a straight jacket made out of a tarp and a belt. I wonder how long this would last—but it’s still a classic MacGyver hack. This blog would probably be better if I included pictures. Oh well.

Space blanket as chaff

A space blanket is basically a thin mylar sheet. It has a nice property in that it reflects infrared radiation. The idea is that you cover yourself with this and when your body radiates infrared light, it reflects it back to your body.

Can you use this as a countermeasure against a ground to air missile? Maybe. Of course there are two types of missiles. There is the heat seeking missile and the radar missile. For the heat seeking missile, it is guiding by the giant infrared source—the engine of the aircraft. It’s a least plausible that this space blanket could block the infrared light from the helicopter enough to confuse the missile. Possible.

If the missile is radar guided, then you can block the radar that comes out of the missile. This is the idea behind chaff (a real thing). It’s basically thin strips of metal that fall in the air behind an aircraft. The metal spreads out and can make a large radar reflection such that the missile thinks it’s a target.

Would a space blanket work? It’s possible. Really, you want metal—but this might work at least a little bit.

Splint and crutch from helicopter parts

Classic MacGyver stuff here. Nothing else to say.

Clean water from a tree

Can you get clean water from a tree? It seems like this is legitimate.

Dried wood as a desiccator

This seems like a plausible way to dry out a wet phone. It would take some time though.

Swiss Army Knife as a signal mirror

MacGyver uses the blade on his knife to attempt to reflect sunlight towards a rescue helicopter. I’m pretty sure this would work.

As a side note—I’ve been thinking about the brightness of light reflected from a mirror (for another project). It seems like this is fairly difficult to calculate. Perhaps the best way is to just experimentally measure the brightness of reflected light. I guess I will do that at some point.

Tree sap and a battery to start a fire

If you want to use a battery to start a fire, you need an electrical conductor. This allows electric current to flow from one terminal of the battery to the other. It’s this electrical current that can make things get hot—hot enough to catch on fire.

So, the battery part is good. What about the tree sap? Yes—apparently, it is indeed a conductor. There you go, a fire.

Distance to lightning strikes

This is another reminder. I should write a post about how to estimate the distance to a storm. The short answer is that when lightning strikes it produces both light and sound. The light has a super high speed, but the sound is just fast (not super high fast). This means that the light gets to the observer first. By counting the time between the “flash” and the “boom” you can estimate the distance.

I thought I had already blogged about this—but I can’t find any such post.

Creating a homemade capacitor to store charge

Here is the short version: MacGyver makes a DIY electrical capacitor (a Leyden jar) to get some electrical charge from a lightning storm. He then uses this to power the satellite phone.

The Leyden jar is totally real. Honestly, I was surprised at how well this worked. Check it out.

Finally, you can make something like this yourself.

Zipper as an wire

MacGyver uses the zipper to make a complete circuit from the battery to the sat phone. Would this work? It’s tough to say. In order to get an electric current, you need a closed circuit with a conductor the around the whole path.

Parts of a zipper are clearly conductors (the metal parts). However, if there are gaps between the metal, then it wouldn’t work. If you zip the zipper, there should be contact—at the very least, this is plausible.

# MacGyver Season 1 Episode 12 Science Notes: Scissors

Stove Bomb

MacGyver needs a distraction to escape from a cabin in the woods (surrounded by bad guys). He puts some chemicals into an iron stove and rolls it out the door.

The stove explodes when someone shoots inside of it—it’s not because of the spark from a bullet (because they don’t really do that). No, the bullet has to puncture the can of stuff in there to mix the chemicals. That’s what causes the explosion.

Also, a quick note—that stump remover is some bad stuff.

Cheese puffs to get past phone lock screen

How do you find someone’s pin code? MacGyver crushes up some cheese puffs and sprinkles them on a phone screen. The oil from someone’s fingers leave some residue that makes the cheese puff crumbs stick to the phone.

Now you know which numbers are used in the pin code—you still have to figure out the order (and this case it was three numbers so there was one used twice). But MacGyver figures that it’s an important number.