A few lessons ago, we had an activity on propulsion. This is to get us a better understanding on how propulsion works in engines. For that activity, we were given a few materials, paper, scizzors, balloon and a ping pong ball. Our main objective is to propel the ping pong ball as high as possible using the limited materials provided.
We had a few ideas. Our first idea, was to use the paper cone as a funnel, then use the air in the balloon to propel the ping pong ball upwards, just like the engine of a jet fighter. When it uses after burner, the ends of the engine will cave in, creating a smaller hole which will produce more energy to push the plane forward. We rolled the paper a few times, trying to find the better size for the funnel. In the end, we settled for a shorter funnel length, thinking that the distance will be short enough for the air to propel the ball upward. The longer the length, the further the air has to travel, which will lose energy as it travels.
But it turns out that the structure for the funnel was not strong enough for it to last when we release the air in the balloon. Thus it made us realize that we need a strong structure to sustain the energy of the air coming out of the balloon.
Our next idea was to stick the ping pong ball at the mouth of a full blown balloon, then squeeze the balloon to force the air out of it, which will shoot the ping pong ball forward. With the amount of air in the balloon and the amount of pressure that was exerted beneath the ball, it should be able to generate enough lift and energy to push the ball into the air, but we failed to be able to carry out our idea. The ball refused to move no matter the amount of pressure we generated on the sides of the balloon.
In the end, we put in too much strength on the balloon until it burst. Even though we failed and had a good laugh about our mistakes, we did learn that the main reason why our second idea did not succeed was due to friction and resistance. The balloon failed to shoot out despite the pressure was due to friction that prevented the balloon from moving.
Thus this propulsion activity taught me a few important things. The structure must be strong enough to be able to hold the air inside and friction will reduce movement.
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