Sucking lorries

[Miss Zippy]

Whenever I drive past a lorry on the motorway, why does my car appear to be almost 'sucked' towards the lorry? This 'phenomenon' is more pronounced the faster I am going (within the legal limit of course). Is there some scientific explanation for this, or am I imagining it and I'm just a cr*p driver?

[sft42]

Yes it is really happening (you want to feel it on a motorbike as well!!!)...if you ever watch Formula 1 then you'll have heard this explained as slipstreaming basically the vehicle in front is punching a hole through the air in front and then creating a low pressure area behind it which drags vehicles into this zone...the faster the vehicle is travelling the bigger the hole in the air......this is a poor explaination of the effect but if you want anything more just type slipstream into google and any of the motorsport pages that come up will go into great detail if you want it.

[gilf]

Its actually a 2 stage effect both sucking from the lorry but also as the air in front is being moved by the lorry there is less resistance at the front of your car. Its really fun on a motorcycle, but of course very dangerous.

[cupra]

....even more fun on a racing bicycle on a narrow road...!

[Miss Zippy]

Think I shall stick to experiencing the old slipstream phenomenon on four wheels!

[KARL]

A simple explanation is that the air between your car and the large vehicle is travelling faster than the air on the far side of you and this results in a (very slightly) lower atmospheric pressure on the lorry side than the other. This is exactly the same phenomenon as on the two sides of an aircraft wing: The air has to travel a longer distance over the top side (curved - convex) than the underside (flat) so the lower air pressure above gives rise to lift and away you fly (once going fast enough to lift off).

[nona suomy]

In the film Days of Thunder, Tom explains this to Nicole while they're in bed. I think he uses a couple of matchboxes to demonstrate on her thigh - ooo er lucky leg.

[sft42]

Em isn' that exactly what I said then Karl?

[KARL]

Sorry if I upset you sft42, that was certainly not my intention. You may have meant what I said but I don't think you quite did - this is not a competition so let's just leave it at that.