wave nature of matter

[dotcom]

1. The problem statement, all variables and given/known data

A Cadillac with a mass of 2000kg approaches a freeway underpass that is 10m across. at what speed must the car be moving, and how long would it take to go the 10m, in order for it to have a wavelength such that it might somehow diffract after passing through this single "slit"? How do these conditions compare to normal freeway speeds of 30m/s?

2. Relevant equations

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3. The attempt at a solution

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well, I have no idea how to solve this question...
first of all, I cannot imagine what's going on here, partly because i'm not a native english speaker...

Can someone teach me the way to solve this, in detail?
the answers are 3.3*10^-38 m/s and 9.6*10^30 yr.

[Dick]

I really don't see the point of this exercise - but they want you to use the de Broglie wavelength=h/p (where p is the momentum). Just set wavelength roughly equal to the 'slit' size of 10m and figure out v. Then figure out how long it would take you to cross 10m at that velocity.

[dotcom]

ah-huh, i kind of understood the question now.
Thank you!