MacGyver Season 4 Episode 4 Science Notes: Windmill + Acetone + Celluloid + Firing Pin

Egg Drop

It’s not really a normal “MacGyver-hack”, but the egg drop does have a bunch of physics in it. Oh, you’ve never heard of this? Well, it’s a fairly common activity in science classes. Basically students build “something” around an egg so that they can drop it from some particular height and the egg won’t break.

There are a whole bunch of extra rules—like “no parachutes” and “no rockets” and stuff like that. It’s all good fun (mostly). But what about the physics?

Most stuff that breaks on impact are the result of high accelerations from differential forces. If the egg (or any object) is being pushed on one side more than the other with some force (like from the floor), this differential force breaks the material.

Now for some real physics—the Momentum Principle. This says that the net force on an object is equal to the time rate of change of momentum where the momentum is the product of an object’s mass and velocity.

\vec{F}_\text{net} = \frac{\Delta \vec{p}}{\Delta t}

\vec{p} = m\vec{v}

If an egg is going to hit the ground, you know the change in momentum. It’s going to have some initial value and then it will stop. You can’t change this. But you CAN change the time. Let’s write the Momentum Principle in a different way:

\Delta \vec{p} =\vec{F}_\text{net}\Delta t

So, how do we get a particular change in momentum? You can think of two extreme cases:

  • You can have a VERY LARGE FORCE with a very small time interval.
  • You can have a very small force with a VERY LARGE TIME INTERVAL.

Of course you could go somewhere between these two—but you get my point. This is how the egg drop works. You want to build something that INCREASES the impact time so that you get a smaller force.

Why study science?

MacGyver is right. Scientific thinking is problem solving and critical thinking. These are good in any field—not just physics or working at a “think tank”. So, yes science is good for you. But that’s not why you should study it.

Science is one of the things that makes us human. Some of the other human things that we do: art, music, literature, sports, writing and video games (maybe). So, humans should study things that makes us human. That’s why you should take physics (and art).

One last science comment. The Physics Honor Society has this great page on hidden physicists. These are people with degrees in physics that have jobs that might not be labeled as “physicist”. It’s great.

Compound Lever

The keys to all simple machines are force and the distance a force moves. If you apply a force over a greater distance, you can produce a larger amount of energy (to lift stuff or something). This is how a basic lever works. You put a stick on a pivot.

The compound lever is just a way to get the push down force to move over a greater distance. Basically, it’s a lever connected to a lever. It’s lever-inception.

Hoist Lift

Here’s another way to lift something heavy—like a WWII bomb. You can use a hoist. It’s essentially the same idea as a lever except that stuff is hanging from it.

Tri-wheel Stair Climber

This is real.

Of course you can make it more MacGyver-ed by adding a power source. Mac uses some cordless drills to assist with the climb. Oh, you don’t think that would work? Well, if you have a big enough battery you can move anything up the stairs—it just might not be very fast.

Bomb Egg Drop

Putting a bomb in a box with bungees might work. As the bomb-box hits the ground, the bungees will stretch and INCREASE the time that it takes the bomb to stop—thus DECREASING the impact force. It doesn’t matter if it’s a bomb or an egg, it’s the same physics.

OK, you want to win at the egg drop competition at school? Here’s a great video from Mark Rober looking at some of the best egg drop options.

4 thoughts on “MacGyver Season 4 Episode 4 Science Notes: Windmill + Acetone + Celluloid + Firing Pin

  1. Given the emphasis on blunting force by increasing interaction time (egg drop), why were the Phoenix team members not wearing hard hats in the unstable building (unlike the real rescue workers)?

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