The basic idea is to package an egg so that it will not break when I drop it off a roof (assume 10m tall). The packaging should be as small and lightweight as possible. I know using a fluid will be rather heavy, but I'm still curious about his. How would I determine the optimal fluid to use? I know I would want it to move as much as possible to reduce the force on the egg's shell as it decelerates. Of course I would not want the egg to hit the walls of the container, though. I'm thinking I would want a fluid with an appropriate yield stress to almost match the breaking force of the shell, and then have a low viscosity so that it can decelerate significantly. Does this sound correct? Should I think about other stuff? PS: My high school sister is doing the drop. I'm just curious.