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Author | Topic: Physics Question (Sort Of) |
GMx Super Geek Posts: 115 |
posted August 08, 2002 07:21
I was watching the Clint Eastwood/Dirty Harry movie The Dead Pool last night and there was a scene in it that is still bugging the hell out of me. The killer had used a radio controlled car to blow up someone's car as he was backing out of his driveway. He had the controller attached to his dashboard to control the car which was filled with C-4, then detonated it as the toy car slipped under the victim's car. No problem with that, the victim's car was moving slowly as he backed out of the driveway. Later, the killer uses the same kind of radio controlled car to try to kill Dirty Harry. He sees the car, catching on to the fact that a toy car had been used to blow up the last victim, because he found a wheel from the car at the scene. Now, here's what's bugging me-Dirty Harry screeches off, and they begin a high speed chase through the streets of San Francisco. The radio control car is able to keep up with Dirty Harry although he is flying through the streets. the killer is following in his car, controlling the toy. What I want to know-is this possible? I mean if the killer's car is able to keep up with Dirty Harry and the radio signal is still transmitting in front of the car, can the radio controlled car also keep up at the same speed? What would be the formula for that? Try to keep it simple, because I've only had basic Physics, and I didn't do too well in them anyway. Would it have something to do with the velocity of the car that had the controller in it? ------------------ IP: Logged |
Danapoppa Geek Apprentice Posts: 45 |
posted August 08, 2002 07:29
I vaguely remember seeing this movie, and the short answer to your question is, I dunno. I'm wondering instead about the size of the wheels on the remote controlled car, and the speed with which that little motor would have to be turning over. Are there remote controlled cars that can move that fast? IP: Logged |
GMx Super Geek Posts: 115 |
posted August 08, 2002 07:37
quote: The tires seemed to be maybe about an inch or an inch and a half in diameter. Don't know how big the engine was. I don't know how he could have fit a big one in there and still have room for the C-4. It was a Corvette, though. ------------------ IP: Logged |
spungo Highlie Posts: 697 |
posted August 08, 2002 07:40
Yeah, this is an engineering question - I have seen remote controlled cars do up to 100mph... pretty hard to find, though. As for the signal from the controller - it wouldn't make much difference about it's motion - a little bit of a Doppler shift in frequency... but not a great deal... it would only be a problem if the distance between them is near the edge of it's range. EDIT: in fact, if they are both moving at the same speed in the same direction, the effective range is increased as there is no Doppler shift (as ordinarily, the controller is stationary and the car is moving). This is only true if the tuning circuit in the controlled car is exactly matched to the peak frequency of the controller signal. ------------------ IP: Logged |
GMx Super Geek Posts: 115 |
posted August 08, 2002 07:54
So, I guess it was possible. Thanks. I just wondered because you know how Hollywood sometimes doesn't really think these things out. ------------------ IP: Logged |
snupy Highlie Posts: 746 |
posted August 08, 2002 08:57
quote:
IP: Logged |
spungo Highlie Posts: 697 |
posted August 08, 2002 10:06
Oh, Lord. The flames of Hades await us both. ------------------ IP: Logged |
Tau Zero BlabberMouth, the Next Generation. Posts: 1762 |
posted August 08, 2002 10:47
The short answer:� In theory, it could be done.� In practice, it would be so difficult as to be implausible.� (But then, Hollywood is where they dreamed up effects such as people being hit by arrows flying up in the air and through walls, as in The Scorpion King.� Hollywood and reality intersect, but only by accident or lack of budget. ) Doppler shift isn't an issue. Even at pursuit speeds, the frequency shift would be measured in hertz. (50 meters per second divided by, say, 4 meters per cycle = 12.5 cycles per second. You'd need some mighty specialized gear to notice.) IP: Logged |
snupy Highlie Posts: 746 |
posted August 09, 2002 04:02
quote: You, me, and Zorro.Hmmm.... IP: Logged |
Zwilnik Assimilated Posts: 426 |
posted August 09, 2002 05:58
on the speed issue, it could have been a petrol engined R/C car (although it looked more of an electric motor job, we can put that down to movie magic), which would be more sensible than an electric motor as it would be one less electrical signal that might accidentally set off the C-4 as you're starting it up. It would also give the assasin better range. The only downside is, petrol engines are pretty noisy, even the really nice 4 stroke ones, so it wouldn't exactly have been stealthy. IP: Logged |
GMx Super Geek Posts: 115 |
posted August 09, 2002 06:42
quote: It sounded like it was an electric. But it was pretty fast. In one part of the scene, the cars rears back on its back wheels and peels out! ------------------ IP: Logged |
mcgyver27 Single Celled Newbie Posts: 1 |
posted August 09, 2002 11:05
Hi everyone, Unmodified, electric R/C cars (1/10 scale) can go up to 45mph. Unmodified, gas R/C cars can go up to 60mph. I have seen custom built electric R/C cars that have gone up to 110mph. Check out RC Car Action (http://www.rccaraction.com/articles/need_speed3.asp/). I don't recall the exact issue. The only problem with the electric cars is that stock cars only have about 5min battery life. If it is modified the life can drop to 3min. It would have to be a very short chase The one main problem is the power of the Radio control transmitter-most non-licensed ones have a 100-150 foot range so the pursuit car needs to be close to the R/C car. One of the better chase scenes I've seen is the freeway chase from _Runaway_ with Tom Seleck, (I think that's the title) with rocket powered RC cars. IP: Logged |
Steen BlabberMouth, the Next Generation. Posts: 1430 |
posted August 09, 2002 22:23
mcgyver27 wrote: The one main problem is the power of the Radio control transmitter-most non-licensed ones have a 100-150 foot range so the pursuit car needs to be close to the R/C car. Not to defend the movie, since I haven't seen it and I find it difficult to believe someone could pilot both their car and the remote control car at the same time in a chase sequence regardless of technology, I don't think the transmitter would be a problem. After all, if you're going to start sticking C4 in the car blow people up with it, I don't think you're going to pay much attention to FCC limitations on broadcast power. IP: Logged |
ZorroTheFox BlabberMouth, the Next Generation. Posts: 1859 |
posted August 11, 2002 21:03
quote: I think the first one in should reserve the seats, maybe we can get a group discount >;o) ...........Z IP: Logged |
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