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I notice that the larger the truck the greater the magnitude of the lurch. Can anyone give a physical explanation to this?

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1 Answer 1

Bernoulli's principle, the fast moving vehicle drags air with it creating a low pressure region. if you live in a country with high speed trains it's enough force to pull someone off a station platform if the trains don't slow down. (good explanation http://www.physics.umn.edu/outreach/pforce/circus/Bernoulli.html)

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While correct, it is normal when stating causes and effects to call the force the cause and the velocity the effect. For some reason people don't follow this sensible convention regarding Bernoulli's principle. Velocity doesn't cause low pressure--- low pressure speeds air up as it enters. –  Ron Maimon Apr 11 '12 at 7:21
    
The low pressure being the result of air being removed mechanically by being stuck to the vehicle and dragged away seems a clearer explanation than the low pressure causes the air to speed up to maintain some sort of integral –  Martin Beckett Apr 11 '12 at 14:52

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