J.S.
This is normal 2 1/2 year old behavior. That being said, there are some things you can do to cope & minimize them - probably won't eliminate them completley, but it will minimize them. I read a great book with awesome techniques in it called "Love & Logic: Practical Parenting from Birth to 6 Years." There are many Love & Logic books, but the one specifically for this age group is fantastic at giving great examples of coping techniques for exactly these kinds of situations that happen to us every day. I highly recommend it. I've tried it - and although I don't always have the patience to do it perfectly all the time, it makes a HUGE difference when I do. Good luck!