Today i watched as my dog ran around in the yard. When i opened the door to let her in the house, she ran in and wanted to play. She was jumping around and barking, but i wanted to watch tv so i told her to go away. Then she turned around and ran straight into a chair. I have no idea why. Anyway, she was running really fast and she knocked over the chair. After i stopped laughing at her, i realized that if friction could be ignored, momentum would be conserved in this collision. The momentum of Kimi before the collision and the sum of momentums of the chair and Kimi after the collision would be equal.