# MacGyver Season 3 Episode 16 Science Notes: LIDAR + Rouges + Duty

What is LIDAR?

Again, this is not a MacGyver-hack. Well, I guess it sort of is a Mac-hack since he designed the LIDAR. So, what is LIDAR? At the most basic level, LIDAR uses a laser to determine the distance to an object. By scanning this laser over some area, you can get a very detailed distance map. If you know the location of the LIDAR (in the aircraft), you get a very nice map of the terrain below.

But how do you get distance with a laser? The laser produces a beam of light (that’s what the “L” stands for in “laser”) and this light travels at a speed of about $3 \times 10^8\text{ m/s}$. Yes, that is super fast. However, it’s not infinitely fast. So when this laser light travels and reflects off of something, it takes time to get back to the LIDAR. The longer it takes to return, the greater the distance. That’s the basic idea of LIDAR.

How do you start a jet engine?

I’m not an aeronautical engineer (in case you didn’t already figure that out). So here is my very simple explanation of a jet engine. The key to getting thrust is the same as a propeller driven aircraft: make the air coming in go faster as it leaves. This increase of air speed (into and out of the engine) means a change in momentum and thus a forward pushing force. For the jet engine, it increases the final speed of the outgoing air by also heating it by burning fuel.

So, how do you start a jet engine? It’s not the same as starting your car (but not completely different either). The main thing is that you need to get the jet turbines spinning first so that there is air moving through the engine. Then you can add the burning fuel to get the thing started. Here is a great video on how this works. Oh, this is why youtube is so nice—you can find a video on pretty much anything.

Pick lock with a paperclip

Oh, you missed this hack—didn’t you. When MacGyver gets into the old building, he has a paperclip in has hand. So, can you pick a lock with a paperclip? Maybe. You could use the paperclip to jiggle the lock pins, but you would need something to apply torque to the lock cylinder.

Here is a tutorial on lock picking—but don’t be a bad guy.

Break open door with a raft

MacGyver pushes open a locked door by filling a raft with water. Let’s start with the definition of pressure. Pressure is a force divided by an area.

Let’s start with the definition of pressure. Pressure is a force divided by an area.

$P=\frac{F}{A}$

You can solve this for the force.

$F=PA$

So, if you have a pressure (in the raft) it will produce a force equal to the product of the pressure and the contact area. The bigger the area, the greater the force. In fact, with just a small pressure you can get a pretty big force.

OK, this is from a previous episode but I still like it. Here is a demonstration in which I use the pressure from my lungs to lift myself. Yes, small pressure with a large area means a significant e force.

What about the water? Well, the water will give the raft more mass so that it doesn’t just push itself away from the door. If you want to open the door with air pressure, you would need to have something hold the raft agains the door.

Dart gun

I love this visual effect where MacGyver is looking around for stuff to build and it shows all the things he sees. In the end, he builds a dart gun that shoots morphine needles.

Really, I just want to talk about two parts of this build—the shooting and the injecting. MacGyver uses a propane tank to shoot the dart. This is the same as your basic potato gun. Compressed gas from the tank push the dart in the tube. The longer the distance of the tube, the greater the final speed of the dart.

For the injection, you can’t just shoot a needle into someone. You need to push that plunger on the back of the needle to get the drug into a body. That’s where the steel spacers come into play. When the front of the dart hits a person, it will stop. However, the mass on the back will want to keep going until a force slows it down. This force comes from the plunger—that means the plunger gets depressed and the bad guys get drugged.

Beam splitter

How do you make one laser look like many lasers? You need a beam splitter. This is exactly what MacGyver does to fool the baddies into thinking there are bunch of other good guys in the woods.

Basically, a beam splitter is a piece of glass. We like to think of glass as being transparent so that light goes right through it—and it does. That’s why we use glass for windows to see stuff outside. But light also reflects off glass. In fact, if the light (from the laser) hits the glass at an angle then you will get both transmission AND reflection.

It doesn’t even need to be glass. Here is a quick demonstration of a beam splitter with just a piece of clear plastic.

# MacGyver Season 1 Episode 7 Science Notes: Can Opener

Let’s do it.

Ring of fire

MacGyver uses a fire hose to spray gasoline on the ground and then Jack ignites it with a bullet. It looks cool, but there are two problems. One small problem—bullets don’t make sparks (usually)—http://www.cracked.com/article_19781_6-stupid-gun-myths-everyone-believes-thanks-to-movies.html.

Oh, also gasoline doesn’t always burn that well.

OK, but gasoline CAN burn and bullets CAN make sparks—so this isn’t completely crazy.

Fixing an inhaler

MacGyver uses part of a plastic force to fix the part that pushes the release valve of a broken inhaler. This is exactly the kind of thing MacGyver would do.

Battery hydrogen bomb

OK, this is mostly real—but very awesome. Here’s how it works. If you put an electric current through some water, you can break the water into hydrogen and oxygen. In order to do this, you need the water to be able to conduct electricity. NEWS FLASH: pure water doesn’t do this. If you add some salt, water conducts just fine.

Now with the current going through the water, you get tiny bubbles. Bubbles on one electrode (I can’t remember which) are bubbles of hydrogen gas. The other set of bubbles on the other electrode are oxygen.

You can seriously do this on your own. It’s really not hard.

But how would you make an explosion? You can let the hydrogen and oxygen gas mix together—nothing will really happen until you get a spark to star the reaction between the two gases at which point BOOM.

So, in the case of MacGyver he wants to let the hydrogen gas collect at the ceiling. Yes, the hydrogen gas would rise but it’s also difficult to contain. Any tiny crack and it’s gone—but still, it’s a good idea.

What about the ignition? A spark will do. Yes, you can indeed get a spark from a fluorescent light. Especially from the ballast since it makes a high voltage.

Oh, one more comment. What about the 2 psi pressure difference? Is that possible? Probably. Would it knock the door off? I think so—especially if the pressure change is quick. Would it be bad for humans? Could be.

Morse code with the tail lights?

Totally legit.

Final breakout part 1: making liquid nitrogen

OK, this is a stretch. MacGyver uses a carbon dioxide fire extinguisher and some alcohol to make liquid nitrogen. It doesn’t say liquid nitrogen, but that’s what it is (from the air). Let me just show this video:

See. It’s possible. It’s not easy, it’s possible. What about the dry ice? Well, that’s another stretch. Expanding carbon dioxide from a compressed tank CAN INDEED make dry ice. In fact, that’s how we do it in chemistry sometimes.

Final breakout part 2: breaking steel

MacGyver takes the liquid nitrogen and puts it on some steel bars. The get super cold and breakable. The first problem: you would need a lot of liquid nitrogen to cool off the metal. But OK. The second problem—there really isn’t another problem. If you get it cold enough, I think it would work.

# MacGyver Notes Season 3 Episode 9: PAPR + Outbreak

What the heck is PAPR?  It’s an acronym.  It stands for Powered Air Purifying Respirator.  It’s a thing people wear when the are around bad stuff—like a deadly virus.  OK.  Let’s get to it.

Glycerol Lock Hack

Technically, not a “MacHack” since MacGyver didn’t do it.  I’ll proceed anyway.  So, the bad person replaces the mouse lock with a piece of solid glycerol.  Glycerol has a melting point just below room temperature (18 C).  So, in this room it would take a little time to melt.

When the glycerol melts, there is no longer a “pin” holding the door closed and the mice escape.

What other substance could the guy use?  What about something like chocolate?

Positive Pressure

Again, not technically a hack.  If you want a hazmat suit, you want it to be at positive pressure.  Positive pressure means that the interior of the suit is at a higher pressure than outside the suit.  The nice thing about positive pressure is that if the suit gets a hole, the positive pressure pushes the air in the suit out of the suit.  This makes it very difficult for an external virus to get in the suit even if it has a hole.

Sometimes, it’s better to have negative pressure.  In chemistry labs, they use things called “hoods”.  These are essentially enclosed areas that vent to the outside of the building.  They allow a chemist to run an experiment and reduce the risk from fumes.

A hood is at negative pressure.  This means that when the hood door is open, there is air going INTO the hood from the room. That prevents the chemicals inside the hood from getting out.

Oh, here is a video showing the difference between positive and negative pressure.

Detecting Hydrogen Peroxide

The bad guy (again, really he just makes bad decisions—maybe he is not bad, but who am I to judge) uses hydrogen peroxide to dye his hair blonde and to elude the team.

MacGyver then needs to make something to detect this hydrogen peroxide from his hair as the baddie sat in different taxi cabs (OK, the guy has to be bad—who still uses a taxi?).

OK, there is indeed a method to detect hydrogen peroxide and one method does indeed involve a compound from horse radish (yes, that’s weird).  I don’t think it would just turn red, but there would be an interaction between the chemical and the peroxide that could lead to a detection.  It would probably involve illuminating it with a UV light and seeing it change colors.

Battery hooked to a door handle

Again, this isn’t directly MacGyver’s hack.  Instead, Riley sets up a trap—but she said she learned it from MacGyver, so I guess it still counts.

In order to slow down a baddie (different bad guy) she takes a car battery and connects one terminal (I think she uses the positive) to the door handle.  In order for this to work, she has to also connect the negative battery terminal to ground (or something like that).

When the baddie grabs the door handle, he gets shocked.  The key here is that there must be a complete circuit formed when the dude grabs the handle.  That means the negative terminal of the battery would have to also connect to the guy somewhere so that there is a path for the current to flow and shock him.

One way to get this to work would be to have another small wire near the bottom of the door that is connected to the battery.  When the baddie grabs the handle, he also hits the wire—thus making a complete circuit.

Another option would be to use a puddle of water under the door with the negative terminal connected to the puddle. Of course, the dude would need to get wet—so normal shoes might prevent this.  Personally, I like the small wire sticking out option.

Air Wedge

Yes, air wedges are real.  You take this flat bag and stick it in a door—they are usually used for car doors.  When the wedge inflates, the car door is pulled back a little bit—enough to get a stick through the opening to open the lock.

Would this work with a normal door?  Why not.

# MacGyver Notes Season 3 Episode 8: “Revenge + Catacombs + Le Fantome”

SQUID Device

This stands for Safe Quick Undercarriage Immobilization Device (SQUiD).  How long did it take someone to come up with that acronym?  Awesome job.  MacGyver’s version consists of a chain type thingy.  When a car passes over it, the chain hooks on to the axle and wraps up.  This would stop the car.

OK, it would’t flip the car over.  It would stop the front wheels and the car would skid to a stop.  But doesn’t the flip look cool?

Actually, that’s a great physics question.  How fast would a car have to travel such that a sudden stop would flip it over? That’s your homework.

Methanol fire

Yes. Methanol burns—and you can’t really see it.

Carbon Dioxide Putting Out Fire

Fire needs three things: fuel, heat (to start), and oxygen.  If you take away the oxygen, you take away the fire.  If you replace the air (which has 21 percent oxygen) with carbon dioxide, the fire goes out.

So, in this hack MacGyver uses some CO2 tanks to fight the methanol fire.  Yes, an exploding tank would put this fire out.  Oh, but it would also make it hard for a human to breathe.  Better hold your breath.

Pick a lock with a knife

This is theoretically possible.  If you stick something in the lock and use enough torque, it’s possible that the pins in the lock could break.  But otherwise, you need to jiggle the pins.

Comeback Can.

Real.  You can build one yourself.  You should.  Do it.

Chemical Detector

MacGyver puts a chemical detector on the comeback can.  When it rolls down the hallway and back, he can check if it contacted explosive chemicals.  This is very plausible—there are several ways you could make chemical detection paper.

Tarp Bomb Lift

MacGyver uses a tarp under a bomb with a rope over a rafter in the ceiling to lift a bomb.  A couple of notes.

• If the rope just goes over a rafter (no pulley), you would need as much weight pulling down as the weight of the bomb.  Since two people are pulling, this is at least plausible.
• A pulley would be better.  A full explanation.
• Actually, there is a cool physics problem here.  If Riley and Bozer pull at an angle, how much can they lift without sliding towards the bomb?  Don’t do this as a homework problem, I’m going to do it.