Our initial idea was to roll the paper into a cylinder, and used it as a medium between the balloon and the ping pong ball. When the air was released from the balloon, the air travelled along the cylinder and pushed the ping pong ball upwards. However, the ping pong ball only floated upwards for a moment before landing back down to the paper. The distance that the ping pong ball travelled upwards was minute.
Then our lecturer suggested in using a smaller paper to roll into a shorter cylinder. We proceeded, cutting a small portion from the A4 paper, rolling into a cylinder, before securing it with scotch tape. We also secured the balloon to the paper cylinder with scotch tape, to minimize the air being released directly outwards to the surrounding. We released the air from the balloon, with me pressing the balloon to give additional force to the expulsion of air from the balloon. The ping pong ball, propelled by the thrust of the air from the balloon, floated upwards by a few centimetres and maintained its altitude for the duration of the expulsion of air from the balloon.
From this exercise, I can conclude that; One, the shape of the medium between the balloon the ping pong ball affects propulsion. By using a straight cylinder, air travels with minimal air friction and travels using the shortest distance possible, resulting in more propulsion.
Two, Using a shorter cylinder means a shorter distance for the air to travel from the balloon to the ping pong ball, which results in lesser air friction and more propulsion. Three, the speed or the rate of the air that was released from the balloon affects the amount of thrust. By pressing the balloon when releasing air from it, I am giving more pressure to the balloon. Therefore, the balloon releases air at a slightly faster rate, resulting in a higher thrust.
The propulsion can be made more effective by heating the air in the balloon up.
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