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Two cars travel at 53.5 mph when the train leaves the station at 6:01 PM.
How much change will Sally have if grapefruits are 4 for $1.00?
I’m not sure how my parents got through word problem homework with me without massive doses of Valium. Maybe they didn’t. I’d cry, pull my hair, have panic attacks. All of it. The actual math wasn’t really an issue, it was figuring out what the damn equation was supposed to be. I could be asked to speak off the cuff about isolation, gender ideals, and the need for order over chaos in the works of Virginia Woolf and would not break a sweat; but you want me to figure out how many baseballs Dan would have if he gave three to two people, one of whom is three times the age of the other, you will make me cry heaving snotty rivulets of tears.
It’s important to know about my little issue because you’ll need that background to attempt to understand the conversation my husband Chuck and I had last night. You might also want a drink. You see, it started innocently enough–AS IT WILL– with an episode of MythBusters.
To try to cut to the heart of an excruciatingly long story, they wanted to know if two cars crashing into each other at 50 mph would equal the damage done to one car hitting a wall at 50 mph. In a previous episode, one of the guys had said that the two cars hitting at 50 mph was actually like one car hitting a wall at 100 mph. You with me? Seems cut and dried, yes?
If you answered in the affirmative, we clearly have not met.
My problem was the use of the words “force” and “damage” interchangeably. I got way confused. Allow me to attempt to recreate part of our conversation for you.
Me: Okay, what’s with the clay?
Him: (clears throat) They need a control. They’ve constructed a model where two cars will hit each other at 1x speed and 2x speed. The clay blocks on the cars will be measured to see how much compression each block has at the end to see if you have to crash a car into a wall at 2x speed to equal the compression of two cars at 1x speed.
Me: Okay, but what about surface area? Or that cars are made to crumple and aren’t as rigid as a steel wall?
Him: What’s that got to do with anything?
Me: If you hit a stuffed teddy bear with a car…
Him: Where did you get a teddy bear?
Me: …you won’t have the damage you would if you hit a wall regardless of how fast you were going.
Him: That’s not what they’re doing.
Me: They said they’re trying to find out if the damage of two cars hitting at 1x speed is the same or half the damage of a car going 1x speed into a wall. The damage depends on what’s hit. Hitting a teddy bear at 50 mph isn’t going to do a lot of damage to your car.
Him: No, they are hitting either another car or an immobile steel wall. (Does this thing with his hands that I recognize as a non-verbal signal he’s about to go all cage match on me)
Me: But what’s the point? The damage is dependent on what the car hits. Hitting a wall…
Him: I swear to God if you bring up a teddy bear again, I’m walking out.
Me:…I’m not trying to argue with you. I’m trying to understand the experiment. I’m saying the only way to quantify if the damage is the same is to take apart the cars and examine them piece by piece.
Him: What in the hell are you talking about?
Me: The clay blocks attached to the car analogs have flat surfaces. The wall is a flat surface. So the surface area you hit is the same every time.
Him: That’s why it’s the control.
Me: But two cars aren’t flat.
Him: No, stop it. That’s not the point.
Me: How is that not the point?
Imagine this goes on another fifteen minutes or so before we get into the car where it goes on another forty-five. Essentially, it’s more than an hour of Chuck repeating his first statement up there and my attempt to decipher what sounds exactly like the Attic Greek I do not speak. There’s much discussion about resistance, impact zones, equal and opposite reactions, crumple zones, and while I did not drag a teddy back into it, I did bring up a utility pole. Chuck also was thinking of a utility pole, but for a totally different reason.
I look up the experiment on my phone while he runs into his store to drop something off. I try further to explain my bewilderment while we return a bathroom faucet to Lowe’s. Then, while at Walgreen’s, it hits me.
Somewhere force and damage have been used interchangeably in the discussion, but the experiment is (rightly) treating them as two different things.
Me: OKAY!! Here’s the problem. And I bet it’s the SAME problem the nerds had. Force is not the same as damage. Yes, the damage may be similar, but what they’re really talking about is force. Cops always say that the impact speed of two cars is equal to their combined speeds, but that’s not the issue. The force is the force as any good Jedi knows.
Him: Sooo…we’re done now?
The issue is force, and as it turns out, the force of a car hitting a wall at 100 mph is roughly THREE times the g-force of a car hitting the wall at 50 mph while the damage is roughly doubled. That’s because the car is harder to crush the more it gets crushed. Kind of. So, yeah, now I’m done. And I totally get it.
It can’t be said too much: I married a saint.
- Image: Miksang Color by Christopher Cash via Wikimedia Commons and used under Creative Commons license.
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