The Scratch Wiki has many great articles on how to accomplish specific objectives in your Scratch programs, for example:
Simulating Gravity using physics or trigonometry, as well as some simpler methods that work OK for games requiring jumping but are not really very accurate simulations of gravity.
MinecraftEdu comes with some predefined male and female student skins. If you have a skin on your personal Minecraft account, you can use it in class: just choose to log into MinecraftEdu using your Minecraft account. If anyone wants to help make some custom St. John skins (Marymount plaid anyone? Gray hoodies?) , here is a video showing the steps required. Just give me the two image files you end up with for each skin and I will take care of the rest to get it onto our class server.