Someone punches it, the guy punching would probably get a broken fist. Sci-fi purple aside, it's not much different from someone holding an actual wooden or metal shield.
The Omnidroid managed to hit the shield and bend/warp the shere enough to bonk Violet on the head, which caused her to lose concentration.
Plus, shouldn't the force field (and Violet and Dash) simply shoot out in some random direction, like what would happen if one tried to pound their fists on a marble?
What is the deal with Violet's force fields? Near the climax, the Omnibot somehow gets through one of her force fields enough to knock Violet out, even though in other times it was unable to break through.
It's not that easy to try and spot an outlineless shape in the water especially if you're not looking for one.
How does Violet manage to hide underwater using her invisibility? Shouldn't she appear as a large girl-shaped bubble?.
Capes can serve practical purposes such as providing a larger target, aiding in flight for those superheroes capable of it, acting as weapon storage, and allowing for gliding among other reasons. The in universe justification is easily solved by simply the addition of a breakaway clasp on all capes.
The real reason for the NO CAPES is because animating capes is a pain and thus the writers put in this justification so they wouldn't have to put capes on everyone since being a superhero IP it would be expected.
The reason her car crashed was because her excessively long scarf got caught in the wheels of said car and broke her neck.
Isadora Duncan, for instance, died when her car crashed.
Note that even 'ordinary' materials can be decievingly strong.
Admittedly, the only thing capes bring to the table is Rule of Cool, so Edna can be excused for not wanting to incorporate what can be argued as an addition that hinders more than it helps.
The anti-capes mandate by Edna Mode seems more artistic temperamentalism than anything else.
Are the kind of people who insist on having capes (despite the known risks) going to be satisfied if it tears off just because of a supervillain or two? How unstylish!.
Isn't the real cause of all those cape disasters the guy who made the cape out of the strongest thing possible, and also not allowing them to be easily detached in emergencies?.