At this stage, everything is a learning experience. She wants to see if the same thing will happen every time she drops food from the tray. Does the food fall every time? Most importantly, does Mom pick it up and give it back to me? Don't put food on the tray. Hand it to her, one bite at a time. When she goes to drop the food, say, "We don't drop food from the tray." Use a nice tone. You are training her. You must be consistent. It will take time; it is not a one-shot deal. After a while, she'll understand. From this point on, everything you do is teaching her how to be in this world. She needs to know the expectation will be the same tomorrow as it is today. She doesn't know the proper way to handle food now, but after careful, consistent training, she will. Take the time to do it right in the beginning and you will reap tons of rewards later. Just read the questions here from frustrated Moms who have entered into a power struggle with their kids because the proper training was not consistent. Your daughter seems very curious about the function of gravity. Make sure this gets addressed appropriately and she will also be less like to use food and more willing to accept the proper way to handle food. Remember, as Moms, WE create the environment we want for our families, not the other way around!