Community Forums => General-3 => Topic started by: UncleBob on February 24, 2013, 04:39:17 PM
Title: Who's good at sciencey-mathy things?
Post by: UncleBob on February 24, 2013, 04:39:17 PM
So, I have a long, straight stretch of road. I'm driving a car at a steady 50 MPH. In front of me is a vehicle going 49 MPH. The back of this vehicle is a ramp. This ramp goes straight up the back of the vehicle, to a platform that goes over the top and then down the front. Like this: /¯¯¯¯¯¯\
Now, this ramp isn't just a normal ramp - it's like a treadmill. If someone stood on the back of this treadmill and was able to stand up straight when the treadmill started moving (while the vehicle is standing still), they'd go forward at 50 MPH.
So, if I'm going 50 MPH, drive onto the ramp-treadmill-vehicle that's going 49 MPH and the treadmill is rolling at 50 MPH - if someone was standing on the side of the road and used a radar detector to measure my speed - how fast would I be going at the top of the other vehicle?
Title: Re: Who's good at sciencey-mathy things?
Post by: BlackNMild2k1 on February 24, 2013, 04:42:24 PM
you'd be going 49mph...?
Title: Re: Who's good at sciencey-mathy things?
Post by: BranDonk Kong on February 24, 2013, 05:02:29 PM
149MPH...I think.
Title: Re: Who's good at sciencey-mathy things?
Post by: ShyGuy on February 24, 2013, 05:12:18 PM
If your speed goes below 55mph you blow up. BUT if you go over 85mph you time travel back to the future.
Title: Re: Who's good at sciencey-mathy things?
Post by: nickmitch on February 24, 2013, 05:58:38 PM
I think Brandogg is right. You'd move 50 mph relative to the surface you're on (the treadmill), which itself is moving at 50 mph while also being on a platform (the other car) that's moving 49 mph. Right?
Title: Re: Who's good at sciencey-mathy things?
Post by: pokepal148 on February 24, 2013, 06:26:55 PM
you'd be wasting gas
Title: Re: Who's good at sciencey-mathy things?
Post by: BranDonk Kong on February 24, 2013, 08:45:49 PM
Pretty sure you just add them all together since they are all going in the same direction.
Title: Re: Who's good at sciencey-mathy things?
Post by: BlackNMild2k1 on February 24, 2013, 09:08:44 PM
100mph.... ?
I glossed over the part of the treadmill. But this is he Funhouse, and I didn't really take the question serious enough to read it thoroughly.
Title: Re: Who's good at sciencey-mathy things?
Post by: pokepal148 on February 24, 2013, 09:40:24 PM
i dont think physics works that way
Title: Re: Who's good at sciencey-mathy things?
Post by: Stogi on February 24, 2013, 10:56:59 PM
If the treadmill itself is moving 50 mph, it doesn't matter what surface it's on, you would only have to go 50 mph to stay on top of it. The fact that the car is also moving is irrelevant to your question. It's all relative and your speed on treadmill isn't relative to the speed the car. And if you wanted to know what the speed both you and the car are going, well you're on top of the car, so 49 mph.
For instance, we are on flying at damn near a thousand mph simply being on Earth, it doesn't mean I am actually going a thousand mph, though to Mars it would appear so.
Title: Re: Who's good at sciencey-mathy things?
Post by: Caliban on February 24, 2013, 11:01:03 PM
The real question is, what is UncleBob really planning to do with this setup?
Title: Re: Who's good at sciencey-mathy things?
Post by: Shaymin on February 24, 2013, 11:02:26 PM
That would be one hell of a Mario Kart tournament.
Title: Re: Who's good at sciencey-mathy things?
Post by: UncleBob on February 24, 2013, 11:15:10 PM
If the treadmill itself is moving 50 mph, it doesn't matter what surface it's on, you would only have to go 50 mph to stay on top of it. The fact that the car is also moving is irrelevant to your question. It's all relative and your speed on treadmill isn't relative to the speed the car.
Perhaps I wasn't clear on this point - the treadmill would be pushing you forward in the same direction as both vehicles are traveling - not working against you.
Title: Re: Who's good at sciencey-mathy things?
Post by: Stogi on February 24, 2013, 11:17:38 PM
So then you'd have to go in reverse to stay on it? Well if it's velocity you want for the car on top, it's negative 50 mph. If it's both, it's still positive 49 mph.
Title: Re: Who's good at sciencey-mathy things?
Post by: UncleBob on February 24, 2013, 11:22:43 PM
Yeah, you'd have to go in reverse to stay on - but you're not necessarily wanting to stay on. You're wanting to drive off the front of the bottom vehicle.
Title: Re: Who's good at sciencey-mathy things?
Post by: Stogi on February 25, 2013, 12:26:06 AM
Then yes, you would indeed be going faster than 50 mph once you hit the treadmill. It would be as if you stepped on to a treadmill at the airport. Your speed would increase by 50 mph, i.e. a 100 mph if you kept the same speed. Again the car below you going 49 mph does not add to your own speed.
Title: Re: Who's good at sciencey-mathy things?
Post by: ShyGuy on February 25, 2013, 12:29:33 AM
Is it like walking up an escalator?
Title: Re: Who's good at sciencey-mathy things?
Post by: Stogi on February 25, 2013, 12:42:01 AM
Yes, but in this case, we do not have to deal with any incline or decline, since only the speed was given. However, if we were give more facts, you'd have to find the real speed at which the car moves up, over and back down.
In this case, it is more like a car is parked and next to it is a strip of 50 mph treadmill the length of the car. Any speed from another car that reaches the treadmill will simply be added to the 50 mph.
Title: Re: Who's good at sciencey-mathy things?
Post by: BranDonk Kong on February 25, 2013, 01:29:48 AM
You just add the speeds together - just like walking on a people mover. If it's going at 3 MPH (typical walking speed) and you stay still, then you go at 3 MPH, but if you keep walking in the same direction you go at 6 MPH (notice how you pass people that are standing on it. Now, if that was on top of a car that was also going 3 MPH, you'd be going 9 MPH (relative to the ground).
149 MPH for the car, final answer.
Title: Re: Who's good at sciencey-mathy things?
Post by: Stogi on February 25, 2013, 01:39:21 AM
No the car on the bottom does not add to the speed. The car has nothing to do with your speed.
That's like saying that stacking 10 cars that are moving the same speed will make the top car 10x faster. It makes no sense.
Title: Re: Who's good at sciencey-mathy things?
Post by: BlackNMild2k1 on February 25, 2013, 01:52:02 AM
someone put together an illustration.
if the car is moving 49mph, and the treadmill ontop of that car is moving 50mph in the same direction, and then there is a car that drives over that treadmill on the moving car @ 50mph.....
::calculating::
149mph makes sense.
Title: Re: Who's good at sciencey-mathy things?
Post by: Stogi on February 25, 2013, 02:12:12 AM
Ah ok. I'm am thinking how fast you are going from the perspective of Unclebob, i.e. on top of the ramp. If you were an outside observer, then yes, you would indeed be going 149 mph.
Title: Re: Who's good at sciencey-mathy things?
Post by: BranDonk Kong on February 25, 2013, 09:51:48 AM
No the car on the bottom does not add to the speed. The car has nothing to do with your speed.
That's like saying that stacking 10 cars that are moving the same speed will make the top car 10x faster. It makes no sense.
That's only if none of the top cars are moving, they are just sitting there. Not the same thing.
Title: Re: Who's good at sciencey-mathy things?
Post by: stevey on February 25, 2013, 09:29:47 PM
*Assuming a spherical car in a vacuum cruising at 50 mph*
If the treadmill is realistic, it will grind to a halt from lack of torque and so the car will just continue over the other car at 1 mph and continue pass it going at 50 mph. Otherwise the treadmill would seem to be going 49mph to the car and fling it forwards at 99 mph; killing everyone in it. The momentum of the wheels wouldn't add to the speed and the engine torque would be spent on preventing the wheels from spinning backwards.
Title: Re: Who's good at sciencey-mathy things?
Post by: pokepal148 on February 25, 2013, 10:03:51 PM
*Assuming a spherical car in a vacuum cruising at 50 mph*
If the treadmill is realistic, it will grind to a halt from lack of torque and so the car will just continue over the other car at 1 mph and continue pass it going at 50 mph. Otherwise the treadmill would seem to be going 49mph to the car and fling it forwards at 99 mph; killing everyone in it. The momentum of the wheels wouldn't add to the speed and the engine torque would be spent on preventing the wheels from spinning backwards.
exactly the possibility that i was hinting at
Title: Re: Who's good at sciencey-mathy things?
Post by: UncleBob on February 26, 2013, 08:11:06 AM
A wild poll appears!
Title: Re: Who's good at sciencey-mathy things?
Post by: BlackNMild2k1 on February 26, 2013, 11:03:46 AM
Where is the option for 88mph?
Title: Re: Who's good at sciencey-mathy things?
Post by: oohhboy on February 26, 2013, 11:13:38 AM
Since it is all relative, from the observer on the ground it is all the velocities added together since they are all moving in the same direction. The car at the bottom is moving at 49 MPH, a person standing on the trendmill relative to the car at the bottom moves forward at 50MPH resulting in a speed of 99MPH to the stationary observer. A car travelling on top of a stationary treadmill would result in the car travelling in 100MPH, since the treadmill itself is travelling at 49MPH, that is added, so the final speed is 149 MPH.
Assumptions made are that the treadmill and cars have enough power to maintain it's velocity as additional load is placed upon them. Any resulting acceleration is "instant" or the treadmill is of sufficient length to accelerate the top car to it's final velocity. These assumptions are made as there is insufficient information to make more detailed calculations.
An interesting note 149MPH/129.5 Knots is about the top speed of a C172R in level flight meaning the plane could land on the car without changing it's speed. Also if it landed on the treadmill, the plane's speed would not change.
Title: Re: Who's good at sciencey-mathy things?
Post by: pokepal148 on February 26, 2013, 02:04:34 PM
149MPH/129.5 knots uncle bob find a nice interstate highway and test this... what could go wrong :)
Title: Re: Who's good at sciencey-mathy things?
Post by: BranDonk Kong on February 26, 2013, 06:39:10 PM
I think I've earned the title of smartest person on the forums.
Title: Re: Who's good at sciencey-mathy things?
Post by: oohhboy on February 26, 2013, 09:12:37 PM
Your lack of comedy option and extra credit disappoint me.
Title: Re: Who's good at sciencey-mathy things?
Post by: pokepal148 on February 26, 2013, 11:07:58 PM
are we talking how fast your insurance agent moves in the opposite direction maybe??
Title: Re: Who's good at sciencey-mathy things?
Post by: UncleBob on February 26, 2013, 11:25:16 PM
Now, let's put a cannon-like object on the top of the top vehicle. When the top vehicle hits the middle of the treadmill, the cannon-like object fires a projectile that, when stationary, the projectile would reach a top speed of 50 MPH. How fast will the projectile be moving (again, relative to the ground) at top speed?
Title: Re: Who's good at sciencey-mathy things?
Post by: BranDonk Kong on February 26, 2013, 11:53:27 PM
50 MPH.
Title: Re: Who's good at sciencey-mathy things?
Post by: ShyGuy on February 27, 2013, 12:23:29 AM
This thread is frivolous and UncleBob is the worst.
SHOW ME REAL WORLD APPLICATION OR I'M PULLING THE GRANT MONEY
Title: Re: Who's good at sciencey-mathy things?
Post by: pokepal148 on February 27, 2013, 02:08:51 PM
Now, let's put a cannon-like object on the top of the top vehicle. When the top vehicle hits the middle of the treadmill, the cannon-like object fires a projectile that, when stationary, the projectile would reach a top speed of 50 MPH. How fast will the projectile be moving (again, relative to the ground) at top speed?
you suggested the idea i think you should be the one to embark on this scientific endeavor to test all of this
Title: Re: Who's good at sciencey-mathy things?
Post by: Ceric on February 27, 2013, 02:14:26 PM
Now, let's put a cannon-like object on the top of the top vehicle. When the top vehicle hits the middle of the treadmill, the cannon-like object fires a projectile that, when stationary, the projectile would reach a top speed of 50 MPH. How fast will the projectile be moving (again, relative to the ground) at top speed?
I don't think the Projectile could overcome the 49MPH to get out of the tube.
Title: Re: Who's good at sciencey-mathy things?
Post by: BlackNMild2k1 on February 27, 2013, 03:10:47 PM
Now, let's put a cannon-like object on the top of the top vehicle. When the top vehicle hits the middle of the treadmill, the cannon-like object fires a projectile that, when stationary, the projectile would reach a top speed of 50 MPH. How fast will the projectile be moving (again, relative to the ground) at top speed?
I don't think the Projectile could overcome the 49MPH to get out of the tube.
Only if the projectile and its cannon were both launched to their top speeds at the same time. Otherwise the projectile would already be moving at 49+mph inside the cannon before it was launched at 50mph ontop of that speed.
At least I think that's how it works.
Title: Re: Who's good at sciencey-mathy things?
Post by: ShyGuy on February 28, 2013, 10:00:59 AM
Somebody needs to go to an airport with two remote control cars. send them on a race. one will hit the moving sidewalk escalator and the other one will drive outside of it. You can see how well the escalator RC car does in comparison.
