PET Water Bottle Rocket

PET Water Bottle Rocket

Level:

Primary, Elementary, Secondary

Concept

It is easy to understand that rocket fly by using reaction when it pushes away something to outside. PET bottle rocket can fly up to the height of the school roof. Students can have a lot of fun.To enlarge the momentum, water is put

in the PET bottle and it can fly higher than in the case of only the air in it. It can be examined how to make the big momentum. It is understood to be able to make the fog and the cloud, when the adiabatic expansion happens suddenly.

Materials

PET bottle (for a carbonated  drink), rubber stopper, airpump, pin for the ball, water, celluloid board and packing,tape

Fabrication

1. Make a small hole in the rubber stopper, and the pin for the ball is passed.
2. Water is put in the PET bottle about 1/3.
3. The rubber stopper is strongly pushed into the mouth of the PET bottle.
4. Put some air in the PET bottle by air pump.
5. When the pressure in the PET bottle grows more than the frictional force of the rubber stopper and the bottle, the bottle launches.

It is better to use the PET bottle for a carbonated drink because of the high pressure. If the PET bottle is cut and the launch pad is made, it becomes easy to fly.   Put the head corn on the top and wing on the lower part to fly stably.

Science

It hardly flies only by air in the PET bottle.  The water is heavier than the air, so the momentum that is pushed away from the bottle becomes big. Therefore, the rocket comes to fly higher. It is possible to examine the law of conservation of momentum by measuring the height which the rocket flies over.

At  the moment of launching, water goes away and the reaction pushes up the PET bottle rocket.

Extension

Let’s make the fog in the bottle. At the moment when the rocket was driven, it becomes white in the PET bottle momentarily.  It is because the temperature rapidly falls by the adiabatic expansion when an inside gas expands suddenly.

The fog can be made in the PET bottle in the classroom by using this experiment.

2 The small amount of water is put in the PET bottle, and rubber stopper is put.   Put some air in the bottle by air pump.

The fog can be made and it becomes white inside the PET bottle after the rubber stopper is pushed away.   If the smoke of the match is put inside the bottle before the pumping, it becomes easy to make the fog.   It is quite the same mechanism that can make the cloud in the sky.   During the pumping, the air temperature goes up.

After the stopper is pushed away, the adiabatic expansion occurs and the air temperature in the bottle is down. The fog is made.