Group Reflection on Ping Pong Ball Exercise

For the ping pong ball exercise, we were provided with 2 sheets of A4 size paper, a pair of scissors, a roll of scotch tape, a deflated balloon and a ping-pong ball. We were asked to conduct an experiment with the above materials to make the ping-pong ball levitate as high as possible.
The initial idea we came up with was to inflate the balloon and roll the A4 paper into a cylinder. Using the A4 paper as a pipe for air to pass through from the balloon, the ping-pong ball will be placed at the other end of the A4 paper. Then the ping-pong ball will be driven by the force of the air from the balloon and hence be thrusted upwards. First, one of us blew up the balloon till as big as possible while another of us rolled up a piece of A4 paper into a cylinder. Next, we pinched the mouth of the balloon tightly, then we fitted the cylinder into the mouth of the balloon and taped the balloon to the paper cylinder to prevent air from escaping. We then placed the ping pong ball at the other end of the paper cylinder and released our grip on the mouth of the balloon. Initially, the ping pong ball rose by a little bit and then it flew out of track and dropped onto the floor as it was unable to maintain its equilibrium.
We tried the next idea which was to roll the piece of A4 paper into a cone but we did not execute this idea as the opening on one side of the cone is quite big and the air will be able to escape easily.
Our teacher suggested we use a shorter cylinder and we cut the cylinder and tested it out the same way as what we did for the first idea, however the ping pong ball only moved slightly as the cylinder was too long and the air travelling up the cylinder lost its speed before reaching the ping pong ball. Then we decided to make the cylinder shorter so that the speed of the air from the balloon will not be reduced so greatly when it reaches the ping pong ball. We executed this idea and it worked. The ping pong ball levitated at a greater height than before and it was quite stable.
From this exercise, we learnt that the medium created cannot be too long as the air travelling through the cylinder will lose its speed as it travels further up. Another thing we learnt is that the shape of the medium between the ping pong ball and the balloon affects the propulsion. With a straight cylinder, air can travel the shortest distance possible. By using a shorter cylinder, the air resistance will be reduced. Also, by pressing the balloon when it is releasing air, the balloon will release air at a faster rate, thus resulting in a higher thrust.