Hi there. Hopefully I'm posting this in the correct place. I took a look at the guidelines and decided not to post in the general physics forum as this question does seem homework-like, though it's not exactly homework. Just a general physics question if that's alright. If this is the incorrect place to post this question then please tell me so I'll know not to do so in the future. My physics teacher mentioned that if you wanted to throw a snowball at someone in order to hit them with as much force as possible (he said this jokingly and told us not to actually try it out) that you could get inside of a car and throw a snowball out towards your target (such as a person or whatever it may be) as the speed at which the snowball traveled would be equal to the speed at which the car was also traveling. For example: I'm inside of a car travelling 50 km/h, and I decide to throw a snowball out of that car towards a tree. The snowball would also be travelling at 50 km/h, and thus it would hit the tree with force proportional to the speed it was traveling at. Now our physics teacher didn't explain why this would happen, and I searched on Google for possible answers, but to no avail. Could anyone explain the physics behind this? I find the idea interesting and it's been on my mind for the past few days. Thanks.