# MacGyver Season 3 Episode 20 Science Notes: No-Go + High-Voltage + Rescue

There aren’t a bunch of hacks in this episode—so that means I can just write about whatever I want.

This is just classic MacGyver stuff. I really don’t have anything to add.

High Voltage Power Lines

Now we are talking. Why are these power lines high voltage? To answer this question, we need to first think about three things: power, voltage, current.

Let’s start with power. This is the rate of energy change (or in this case, energy loss). For an electrical circuit, the power loss is equal to the product of voltage and current.

$P = I\Delta V$

But wait! There is also a relationship between voltage and current.

$\Delta V = IR$

Where R is the resistance (in Ohms) of some element. Substituting this definition into the power definition:

$P = I^2R$

So, here is your answer. You get more power loss with a greater current. That means the best option is to have low current power lines. But if you want to transmit power—you have to make up for this with high voltage. Boom. There’s your answer. OK, technically these power lines are alternating current and voltage, but the main idea still works.

Next question. What happens if you touch a high voltage line. The answer: not much really.

Yes, if you touch a high voltage line AND something else—like the ground then you will get zapped. The thing that really messes up humans is an electric current running through them. If you just touch one line and nothing else, there is no complete circuit. With no complete circuit, there is no electric current. Oh, this is why those birds can sit on power lines. As long as they only touch that one line, they are fine.

Belay from a lock

The key to a belay is friction. This is actually a pretty cool thing—the more turns a rope has around something (like a post), the greater the friction. You can control the amount of friction between the pole (or padlock in this case) and the rope by slightly varying the amount of rope around the pole.

I think I need to do an experiment to show this—maybe I will do that later. In the meantime, here is a nice tutorial on belays.

Oh, but what if MacGyver wanted to express his anxiety about heights by calculating the impact force if he fell. His calculation might look something like this.

Motorcycle Jump

MacGyver and Desi need to jump a fence with motorcycles. Here’s what he might calculate to find the minimum motorcycle speed to make the jump.

# MacGyver Season 2 Episode 4 Science Notes: X-Ray + Penny

Hydraulic Hammer

OK, it’s not really a hammer. It’s more like a pressure gun. MacGyver hooks up a pressured line from a water heater to a tube with a rod in it. When the pressure is released, it shoots the rod and hits the door handle to knock it out. That’s great.

If you want it to “hammer” back and forth, you need to do something different. Here is a very basic design.

There is still a tube with a rod, but there are two differences. First, there is a hole on the side of the tube. As the rod moves forward (due to the pressure from the hose), it eventually gets to the part where the side hole is exposed. This would allow the pressure to escape and the rod would stop moving forward.

The other feature is a spring. One side of the spring is mounted to the outside tube and the other to the inside rod (yes, there needs to be a small slit in the tube). This spring will pull the rod back into place once the pressure escapes.

I really don’t know if this would work.

Finding Location with Sound.

This one was tough—but fun. How can MacGyver use evidence he collects to go back and figure out his location? In this case, he uses sound.

In air, sound travels at a finite speed. Technically, the speed of sound depends on the temperature of the air—but using a value of 340 meters per second is a reasonable value.

Since this sound speed is finite, it takes some finite amount of time for this sound to travel over a distance. But of course you already know this because you have seen lightning and heard the thunder. The light part of this lightning strike travels at the speed of light (which is really, really fast). However, the sound part of the strike travels much slower. This means that you see the lightning and then hear the thunder later. The farther away you are from the lightning strike, the bigger the time difference between these two signals.

For MacGyver’s case, he is going to use two sounds that start from different distances and at different times, but reach him (he hears them) at the same time. In this case the sounds are from church bells and a fire station. It’s sort of like the opposite of the lightning problem except that it’s totally different.

So, here is what he knows.

• Church bells every half hour.
• Fire station alarm went off at 1:29 and 58 seconds.

That means the sound from the church bells traveled for 2 more seconds than the fire station sound. How far away is MacGyver from the 2 sources? Yes, this is a more difficult problem—but it’s not impossible.

This is what MacGyver writes on the board to solve this.

Now for fun, here is my original solution.

Isn’t that fun? Well, it is for me. Oh, what about the two points? You can think of this problem as two expanding circles. Each circle represents a sound and the circle’s radius increases at a rate equal to the speed of sound. So, one circle is going to be bigger than the other one (because that sound was created first). We are looking for the places where the two circles intersect. Yes, there are two of these locations. MacGyver picks the location based on the direction of water flow in the sewer.

You know, I really should make a python animation for this problem. Maybe I will do that soon. Oh, one final note. For my solution above, I recreated the calculation so that it would have the correct values. At the time, I was at my son’s soccer practice. So this is a picture of my notes as they are sitting on the seat of the car. True.

X-Ray Fluorescence

It’s real. The basic idea is to use x-rays on the film. These x-rays excite some of the atoms in the film such that they fluoresce and produce infrared light. You can’t see the IR light, but a video camera can.

It’s something like this—a technique that is used to look at different layers in paintings.

https://www.livescience.com/13499-hidden-painting-features-xrays-110331.html

As a bonus, I made a short video explaining x-ray fluorescence.

# MacGyver Season 1 Episode 9 Science Notes: Chisel

There is no introduction, just science.

Lighter and spray can stun thing

MacGyver gets a broken spray can of something (it really could be any aerosol can) and attaches a cigarette lighter to it. He then makes it so the lighter burns while the spray sprays. When he throws it, boom.

Yeah, these spray cans can ignite stuff. This is plausible.

DIY hot air balloon for Jack’s phone

Someone needs to make a super clip of all the times Mac says “Jack, I need your phone”. I think that’s funny.

In this case, the idea is to build a mini hot air balloon to lift up the phone so that they can see a “bird’s eye view” of the city. Here’s how it works.

• Get a thin plastic trash bag.
• Get some fuel—in this case it’s that stuff that burns to keep food hot for a buffet or something. Oh, they put it in aluminum foil.
• Hang the phone and light the fuel.

Boom. That’s it. Yes, it’s real. The basic idea is that the fuel heats up air that fills the bag. Hot air has a lower density than cold air—this means that the weight of the air inside the bag is less than the weight of air outside of the bag. This gives a net upward buoyancy force on the bag.

Here is a more detailed explanation of buoyancy, if you need it.

OK, but would this be enough to lift a phone? It would be tough, but it’s at least plausible. It depends on the weight of the phone and fuel, the size of the bag, the temperature of the inside and outside air. So, it’s possible.

Here is one you can make yourself.

Bullet proof paper

OK, it’s not bullet proof paper. It’s a calculation of how much paper you would need to stop a bullet. I love how well this turned out.

Bullet proof shield

This one is simple. Yes, if you tape a bunch of kevlar vests to a door it will be fairly bulletproof. MacGyver’s calculation is great (I should know). OK, it’s not perfect—but it’s a good example how to make a basic estimation.

Personally, the dialogue gets to the basic point and the animations and graphics are really nice. LOVE IT.

Let’s go over some of the details.

• You need some basic values—like the speed and mass of a bullet from an AK-47. I googled this, but maybe MacGyver just knew it.
• From there, you want to somehow model the interaction between a bullet and paper. The first idea is to think of it like a drag force (just like a bullet going through air or something). Of course this causes a problem because that makes it a velocity dependent force and therefore VERY difficult to deal with.
• But what if there is a constant force on the bullet during the interaction with the paper? In that case, we can use the work-energy principle (which MacGyver says—YAY!).
• With a constant drag force, you can then find the distance over which this force needs to do work to stop the bullet.
• For the constant drag force, I estimated the density of paper (a little bit lower than the density of water) and assumed this was the constant force. Of course this is wrong—but it’s just a place to start. You have to start somewhere.
• Really, the rest is just calculations.

Here is my original estimation.

Oh, I guess there are a few things to point out. First, the MythBusters also looked at using paper to bulletproof a car. It sort of worked. Second, in the end MacGyver reports the paper thickness in inches. I hate imperial units—but I guess that’s just the way things are.

Still, super pumped at the way this turned out.

Improvised weapons

In order to fend off the attackers, MacGyver makes some improvised explosives to shoot marble cannon balls. I don’t want to go into the chemistry of explosives so I will just put my normal explanation.

Any time you mix two or more chemicals, it is plausible that it could make an explosion. The end.

MacGyver wants to figure out what the bad guys are saying on their radios. He uses a yaghi antenna to get a directional signal and then he connects it to an AM/FM radio and picks up the signal.

OK, they probably don’t broadcast on the AM-FM frequency range. However, it’s possible he could modify the tuner in the radio to pick up their frequency. It would help if he knew their frequency. Also it’s hopeful that they aren’t using encrypted radios.

Dish soap to slide a safe

This is basic physics. Dish soap can indeed decrease the frictional force—especially for smooth surfaces. This would make a great physics problem.

Sugar putty bomb

Again with the bomb thing—using sugar for an explosive. Well, you can make a rocket from sugar (again—from the MythBusters)