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Water-rocket experiments Number 1 Click the arrow in the centre to start the movie. I launch a proprietary 'Rokit' 2-litre-bottle water rocket. A cardboard tube was taped to the bottle to accommodate the supporting launching stick. Also a tennis ball was taped to the end of the bottle to improve stability and cause the rocket to reach a greater height. Release pressure was approximately 40 pounds per square inch. Notice the cloud of spray as the pressurised air inside the bottle punches out past the remaining water. To watch the same movie on the YouTube website, click here. Number 2 Click the arrow in the centre to start the movie. This time I launch an unmodified 2-litre-bottle with the neck stoppered with a soft plastic bung. The bottle is tied to a house-brick with a length of braided nylon cord. Again, release pressure was approximately 40 pounds per square inch. The coloured streamers had been fitted to this bottle by the ITV studio team when I used it it on the 'Ministry of Mayhem' children's TV program. Notice that my face does not lift to follow the launch this time. This explosive launch is so much faster than the one shown in first movie. To watch the same movie on the YouTube website, click here. Number 3 Click the arrow in the centre to start the movie. Close-up view as I launch the same unmodified 2-litre-bottle, again tethered to a house-brick with a length of braided nylon cord. I use this set-up for indoor demonstrations and wanted to see exactly what is happening in slow-motion. The movie revealed some important details. See how the bottle turns vertical apparently in reaction to the stopper being forced away to one side. This explained why I'd previously noticed that the cord needed to be shorter than expected in order to avoid hitting the ceiling. And I really didn't want to hit the ceiling during indoor demos, because the movie also showed that the bottle reaches a velocity of 100 miles per hour almost immediately after lift-off. Finally, notice how the lightweight, empty, but fast-moving bottle actually lifts that heavy brick clear off the ground... To watch the same movie on the YouTube website, click here.
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