Knight Rider Moving Trailer Entry

Quote: Wizard

Hopefully I can get Doc to visit us to chime in, but we had a thread on this at WoV some years ago and I think he will just refer us to whatever he said there.

Quote: Nareed

I think at WoV we discussed that two cars crashing head on while each travels at 45 mph, do not produce a crash equivalent to one car smashing into a wall at 90 mph. This was also on Mythbusters.

http://wizardofvegas.com/forum/questions-and-answers/all-other/19425-riddle-me-this/#post392357

Quote: AZDuffman

Best as I can see is because the ramp is also going 55. Lets look at something easier to grasp. Ever go to an airport with a moving sidewalk? Even if you are at a jog, you do not go flying down the sidewalk. It takes you a moment to catch up with things.

Quote: Ayecarumba

How is dropping the rear end as described above, different than driving onto a moving ramp?

Quote: Wizard

I've asked PhD physicists, including my father, this question, and they always contradict the Mythbusters results.

Quote: Doc

Here’s my interpretation of what happens:

There are two important elements of momentum and kinetic energy that come into play. One involves the car itself, initially travelling just slightly faster than the ramp that it encounters. That is mostly a linear effect, though there is that slight change of direction to go up the ramp. The other involves the rotational kinetic energy and angular momentum in the engine, drive train, and rear wheels.

For those folks who think that the 55mph car will suddenly start travelling something like 55mph with respect to the ramp, that just ain’t gonna happen. It would require a tremendous impulse to accelerate the car like that, something like the net impulse that was needed to take the car from standing still to its 55mph down-the-highway speed. Considering just the aspects of linear momentum and kinetic energy, the big effect will be that the car has to climb a ramp and will need some additional oomph to make that happen. If the “ramp” were a flat platform almost at ground level, the car could be expected to ride right up onto it and (since the car is going slightly faster than the truck/ramp) maybe need some slight breaking to keep from rolling off the front end.

Now the rotational momentum and kinetic energy do offer the potential to drive the car faster as the tires gain traction with the ramp. At the instant of initial contact, the tires will go from having contact with a stationary road to having contact with a 55mph ramp. That’s why I expected to see some skid. Either the tires, axle, drive shaft, etc., will have to reduce their rotational speed as the tires gain traction, or the car will have to accelerate dramatically up the ramp. Unless someone stomps the gas pedal, it’s much more reasonable to expect the drive train to slow down. Keeping one’s foot in the same position on the gas pedal might be adequate to allow the vehicle to climb the slope of the ramp before you have to let off, or you might have to give it a little gas to get up the hill into the trailer body.

Quote: Ayecarumba

I assume this means that with a lighter vehicle, a less forgiving transmission, and sticky tires (e.g. a motorcycle), shooting up the ramp could be a hazard.