Balloon-powered vehicle

My granddaughter –  a sixth grader is charged with constructing a vehicle that will run at least five meters (I am definitely still a yard and inch person.) on the thrust provided by two nine-inch balloons. I claim heroine status: I got the wheel problem solved while she was in the throes of despair and agony and letting me know all about it.

She had the balloon part producing but now something isn’t working right. I have made some suggestions but she shrugs them off. You can’t tell her anything. That is what my father once said to me, “Nobody could ever tell you anything.” I’m sorry, Daddy; I was such a jerk.

Well, here I go . . . into the fray.