Can you collect unemployment if you leave because not able to perform all duties of job?

You usually cannot collect unemployment if you voluntarily leave a job, or if you are fired "for cause."

If you were hired and then found out the job involved something you couldn't do even with "reasonable accomodation" or just didn't want to do and you quit, you probably won't be able to collect unemployment.

But there's no reason you couldn't go to the unemployment office and talk to them anyway, there might be some kind of exception. For instance, if at the time you were hired the job didn't require you to lift 200 pound boxes and suddenly that was added to your job after you'd been doing it for a while, that might be considered "constructive dismissal" (basically, this usually means that your employer wants to get rid of you but doesn't want to have to pay unemployment, so they deliberately make your job miserable in hopes that you'll quit). You generally can collect unemployment in such a case, but the employer either doesn't understand the rules, or hopes that you don't, so that you won't bother to even apply and/or won't try to fight it if they deny unemployment.