Sunday, March 07, 2010

BMW ad: real or fake?

It's the tablecloth trick. But the cloth puller is not a magician or physics teacher. It's a motorcycle.

Objectors suggest the tablecloth in the XXXL stunt is sandwiched between the table and a table-sized plate of glass. The dinnerware rests safely atop the glass, and is never in any danger of being pulled off the table. I wonder if the objectors worked out the force that would be needed to free the cloth sandwiched that way.

Perhaps the stunt is real. And if so, who's to say that any "crotch rocket" with sufficient acceleration couldn't repeat the stunt?

Either way, it's recommended viewing when you cover the trick in class. Real or fake, the opportunity for discussion is rich.


wingman1659 said...

This is done (it looks to me) by having the table set on top of glass or teflon and then having the table cloth under the glass or whatever, hence the "movement" of the glasses. Movement it more like the shudder of the editing to me.
Either way definitely a fake.

Dean Baird said...

Hmmm... armchair physicists who wrap their speculation in words like "definitely" are folks I find it hard to trust.

Based on the evidence presented, I'm not prepared to employ such definitive judgment on the clip's physics authenticity.

Tyler said...

If the tablecloth were under a layer of glass, wouldn't the whole setup on top be more affected by the friction, not less? That's a whole lot more surface area than the individual items. I suppose the layer could be more slippery, but I'm not sure whether that would outweigh the increase.

I can see how it looks a little smooth, but it sounds plausible to me that a motorcycle could accelerate to a sufficient velocity quickly enough to pull off that trick without gimmicks.

X said...

Video editing. The footage of the motorcycle pulling away the tablecloth is superimposed with footage of the silverware and glasses shaking on the table. No physics tricks here - only camera tricks.

Lyla Burnor said...

The motorcycle would need to achieve a certain constant momentum / acceleration in order to make this work. Watching the clip I don't detect much wobble of the place settings. It seems likely that the taller items in particular would show some sign of motion. It could be that the table cloth material is so light and silky that it would take less force to pull it from beneath all that cutlery and china. This is a great candidate for Myth Busters! I think this might be feasible, but not without some "planning."

Frank said...

i've looked around at other discussions and almost everyone says this is fake. however, nobody has mentioned (or possibly haven't noticed) that there's quite a lot of slack in the rope before the motorcycle accelerates. that means by the time the bike is actually pulling on the tablecloth, it has considerable initial velocity. i say it can be done.
btw, great workshop in march and i plan to visit more next year :o)

Unknown said...

If I were to attempt faking this with a glass tabletop, I would make the table itself porous like the table hockey boards that have pressurized air coming up through, so any object atop is actually floating on a thin layer of air with extremely low friction. The glass top could be restrained from drifting from the side opposite the camera. The problem would be to get the tablecloth to stay in place long enough to do the bike stunt.

Mahesh Sutar said...

Few interesting things about this video.
1) The speed at which the motercycle vanishes out of the camera and the speed at which the cloth moves out of the camera. Huge difference.
2) The way the cloth is tide at 3 different places, looks different. a) The initial take of. b) Cloth fluttering as the vehicle is moving and when its stopped at the end.
3) The over exaggerated emotions at the end.

Anonymous said...

Myth busted~