# Launch Tube Investigation

Extracts from this document...

Introduction

## Christopher Andrew. 29 October 2000

## Launch Tube Investigation

### Plan

In this investigation I will be studying the effects of distance on the projection of a ball bearing from tubes of varying lengths. To do this I will set a launch tube at a height and angle, determined in my preliminary investigation. I will then release the ball from different points in the tube and measure the distance over which the ball bearing has travelled. I will measure this distance, in millimetres, from the point directly below the bottom end of the tube to the front of the indentation made by the ball in the sand. I will use the equipment shown over the page. In my preliminary investigation I first decided to determine the height at which to place the tube. I set the tube at an angle of approximately 30º and took two measurements with a tube length of 10cm and 90cm with the tube at heights of 22, 27 and 32cm. My results are shown in the table below.

Preliminary Height Table

Height of launch tube (cm) | Length of launch tube (cm) | Distance travelled by ball bearing (mm) | |

22 | 10 | 126 | 121 |

90 | 268 | 266 | |

27 | 10 | 129 | 124 |

90 | 292 | 281 | |

32 | 10 | 145 | 144 |

90 | 345 | 328 |

From these results I decided to position the launch tube at a height of 32cm from the level of the sand tray, as the results from this height had the highest range so I will notice a larger difference in my results.

Next I decided to determine the angle at which to set the tube. I can work out the angle of the tube using trigonometry. To work out the angle I would first find the length of the side of the triangle opposite to the angle. To do this I would take away the height of the front of the tube (TF) from the height of the back of the tube (TB). Using this figure, and the length of the tube, I can then use the equation;

sinX = o/h.

X = sin-¹o X h

To determine the angle I first set the tube at the pre-determined height of 32cm and took the same results as before but positioning the tube at angles of 20, 25, 30 and 35º. My results are shown in the table below

#### Preliminary Angle Table

Angle of tube | Length of tube (cm) | Distance travelled by ball bearing (mm) | |

20º | 10 | 130 | 128 |

90 | 347 | 350 | |

25º | 10 | 139 | 150 |

90 | 344 | 366 | |

30º | 10 | 140 | 149 |

90 | 218 | 226 | |

35º | 10 | 145 | 140 |

90 | 224 | 231 |

Middle

Kinetic energy = Potential energy

Kinetic energy = ½mass X velocity²

Potential energy = mass X gravity X height

½mv² = mgh

½v² = gh

This proves that mass is irrelevant as it can be removed to leave a balanced equation.

I can rearrange this equation to find the speed that the ball bearing will be travelling when it leaves the tube. I will be disregarding other interfering forces such as friction and wind resistance.

v² = 2gh

v = √2gh

This means that if I know the height of the ball bearing before it begins to move I can work out the velocity. I can use this information to determine the approximate velocity of the ball bearing as it leaves the tube. I predict that the distance the ball bearing travels will increase steady rate as the length of the tube increaces.

### Results

I measured the distance that a ball bearing travelled from a launch tube of different lengths. I took each measurement in millimetres from the point directly below the tube bottom (TB)

Conclusion

### Evaluation

I believe my results were accurate as I measured my results in millimetres rather than centimetres. However, I would have liked to have measured them in smaller units if possible. When measuring results, I measured them from the point directly below the bottom of the tube (TB). I found this point only once, at the start of the experiment, rather than before each measurement. Although I believe that the tube remained in the same place throughout the experiment I can not be sure of this. In order to increase reliability I should have found the point directly below TB each time I measured a reading. My results were almost all reliable. I found one anomalous result. It was the first result taken at 70cm which was approximately 20mm shorter than could have been expected. In further work I could investigate the effects of the angle of the tube would be. I could also experiment with mass to back up the theory, which explains that it is irrelevant.

This student written piece of work is one of many that can be found in our GCSE Forces and Motion section.

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