I remember a long while ago, I was with my 3 brothers trying to make a vacuum cleaner reverse(blow rather than suck). We spent around an hour on it; flipping switches, taking it apart, and trying to figure out how it worked.
Eventually, we got it working like we wanted! A few tricks and it was blowing air out so powerful it pushed my little brother back.
We thought it would be AWESOME if we got this rock and tried to launch it with our new vacuum cleaner discovery. We put the rock in the tube of our contraption and hit the on-switch. In the blink of an eye the rock was gone. My brothers and I all stood and watched as the rock hurled passed four houses... and hits a neighbors window. Needless to say, we made sure to stay inside for the rest of the day. (:Haha