Welcome and the Physics Question
Glenn M: Good morning and welcome to the University of Massachusetts “Uncommon Leadership” program. We're going to have some fun this morning.
Many of you know I graduated from Arlington High School, and Ray Magliozzi was one of my close friends. Ray sat in front of me in most all my classes. In the science classes I would sneak a peak over Ray’s shoulder. Unfortunately, Ray would shift his seat position. He was no help.
I know many of you are avid Car Talk listeners. If you missed last week’s show here is a short audio clip:
The Physics Question
(Banjo music)
(Telephone call)
Ray: Hello. Welcome to Car Talk from National Public Radio with us, Click and Clack, the Tappet Brothers. So, what's goin' on Tyler?
Caller: My question isn't about a car. It's actually a physics question that I have been debating with my dad for well over ten years.
Ray: We may have to call Wolfgang, but go ahead. We'll give it a shot.
Caller: Okay. Here's the setup. There are two cars driving head-on, right at each other. They each weigh the same and they're going ... let's call it 60 miles an hour. Then, they hit each other, head-on. Well, I say that's the same as one car of that same weight going 60 miles an hour, into an immovable wall. And my dad and now my wife -
Tom: Your dad is right, and your wife is right and you're wrong.
Caller: My dad says it's the equivalent of driving a car into a wall at 120 miles an hour.
Ray: I believe that is correct.
Tom: He's right.
Caller: Oh, come on.
Tom: And I just want you to know, I took that physics course, and got in it, are you ready, an F.
Ray: That's why he took it a second time.
Tom: Because Professor Tisza said to me, (in a Hungarian accent), "Mr. Magliozzi, I'm going to do you a favor. I'm going to give you an F."
Ray: Driving two cars at 60 miles an hour into each other is the equivalent, I believe, of driving one car at 120 into an immovable object. Now, if you had a choice of driving into a stone wall at 60 miles an hour, or driving into another car going in the opposite direction at sixty, which would you choose?
Caller: I have to admit, I would choose to drive into a wall.
Ray: Why, though?
Caller: I don't know. That almost seems like an argument based upon emotion. Just 'cause it seems like you're going faster, but when I work out the physics in my head, it seems -
Ray: The head will get you in trouble every time. You'd be surprised how many times it lets us down in a week. Now, we could certainly be wrong, but my impression from high school physics is that it's the equivalent of hitting the wall at 120.
Tom: We're not wrong.
Caller: I'm never going to hear the end of this.
Ray: I know it. Well, we won't tell them if you don't. One of our other four and a half million listeners might. But you're on your own, man.
Caller: Well, you guys, I guess, thank you. I have to eat some crow on this, but that's okay.
Tom: Sorry.
Ray: I think you do.
Tom: See you Tyler.
Glenn M.: I’m going to ask Dr. Jack Wilson, Physics Professor and President of the University of Massachusetts, to give us the definitive answer to this dilemma. Jack who is right here?
President Wilson: Thank you, Glenn. I'm just going to make this short. I'm sorry guys. Wolfgang was right to flunk you. These two situations are the same from a physics point of view. Two identical cars going 60 miles per hour and hitting head-on perfectly square is the same as hitting a wall at 60 miles per hour. Now, it is true you have twice as much energy to dissipate. But, you have two cars that are crumpling to dissipate the energy, so in fact the acceleration the occupants feel is exactly the same whether they hit the wall or they hit the other car.
Glenn M: I think you should have Jack on the program next week.
President Wilson: To tell the truth, when I take my physics hat off, I'd rather hit the wall, because the guy might be carrying a bowling ball on the dashboard or something. A wall rarely does anything unusual. You can kind of rely on walls a lot more than you can other drivers.
Ray: We got a call from Wolfgang Rueckner, who is a professor at Harvard in the Physics Department. Wolfgang says, "Guys, guys."
Tom: And we said, "Oh, oh."
Ray: He essentially gave the exact same explanation that Jack just gave. We're accustomed to being wrong, and it's not unusual for us to give a wrong answer or two or three or four or five. So, there you go. We can take it.