Question: Re-watching the 2009 movie for the first time after answering [this question about shield collisions](https://scifi.stackexchange.com/questions/9312/what-would-happen-in-the-star-trek-universe-if-shields-collided), I noticed the following:

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> *Enterprise* is about to drop out of warp in Vulcan space.
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> Captain Pike: Raise shields, red alert.
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> *Enterprise* drops out of warp, encounters the debris field of the other star fleet vessels and **suffers hull damage due to a low velocity graze against a piece of debris even though its shields are up and fully charged.**
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The shields are capable of pushing interstellar dust out of the way at high impulse (which is relativistic), *and* surviving photon torpedo detonations.

So what happened?

Answer: 
I'd have to watch that scene again - but it could be that the debris was already inside the shield's surface area. 

In other *Star Trek* material (particularly *TNG*, but other series, too), shields appear to be ellipsoid shells around the ship, so it is possible that the debris was already inside as the shield was powering up.

An alternative explanation is that the shield technology at the time of the movie isn't as good as the other time periods we see in *Star Trek* (it is set prior to *TOS*).
I've always attributed this to the *size* of the debris that collided with the ship. As you mentioned, the shields (augmented by the navigational deflector) are capable of deflecting interstellar dust, even at high velocities. 

But dust has a relatively low mass, meaning the energy required to move it out of the way is not very high (relatively speaking). The destroyed starship debris on the other hand, IIRC, was a large section of a secondary hull, a piece of the saucer section. The energy required to deflect this would have been orders of magnitude greater. Also, we don't know what velocity the Enterprise was traveling at, whether it was moving at full impulse or some fraction. This would have played a large part in how effective the shields would have been as well. 

Finally, remember back to the movie *Nemesis*. In the final battle the *Enterprise* is struck by a large section of a Romulan ship. It is not unreasonable to assume that the *Enterprise-E* from the 24th century, built to battle all the baddies of its age, would have had vastly superior shielding technology. Yet even with that advantage, the shields were only *just* able to deflect that piece of debris.