Hold it closed with your fingers and turn in the outlet to prevent air from escaping
Close the outlet with a clothespin
Cut off a piece of straw about 5-10 cm long.
Attach it to the longitudinal balloon with plenty of tape so that the outlet is in the same direction!
Thread the string through the straw
Attach the string to two chairs or other furniture at both ends. A door handle is also well suited.
There can be several meters or even the whole room in between.
Execution:
Remove the clothespin and hold the balloon closed with your fingers.
Bring it to the starting position and release it.
Observation:
The air flows noisily out of the outlet and the balloon whizzes along the string. In doing so, it reaches a remarkable speed.
Tips:
Even without a string, the launch of a balloon rocket is a sensible freehand attempt.
An elongated balloon is particularly suitable.
Explication:
The taut skin of the balloon increases the pressure inside, so that the pressure difference at the outlet pushes air out of the balloon and accelerates in the process.
According to Newton’s third law, this accelerating force generates an opposite, equal force on the balloon, which accelerates it in the opposite direction.
The balloon experiences a recoil. A rocket, a jet engine or the locomotion of a jellyfish works on the same principle.
The outflowing air receives an impulse, the balloon receives the same impulse in the opposite direction (law of conservation of momentum).
