# Water Bottle Rockets

Topics: Rocket, Water rocket, Model rocket Pages: 18 (2647 words) Published: August 27, 2014
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Introduction4
Aim 5
Hypothesis5
Variables5
Apparatus5
Method6
Calculations7
Results10
Analysis of Results11
Discussion12
Conclusion13
Bibliography13
Appendices13
Journal16

Introduction
A water bottle rocket is essentially that; a bottle modified in the image of a rocket then filled with a select amount of water that is pressurised and launched into the air due to the forces pushing the rocket upwards from the launcher. When the completed water bottle rocket is sitting on the launcher, the force of the surface of the launcher pushes the rocket up whilst gravity drags it down. As the fluid inside the rocket is pressurized, the forces become unbalanced and release the clamps that are holding back the rocket. The fluid will then be expelled through the small opening at the bottom of the rocket (the bottles nozzle) at a fast rate in one direction and therefore providing a lot of thrust into the other direction, allowing the rocket to propel upward. This force will continue to thrust upwards until the last of the fluid is expelled from the rocket (Moore, 2014). To increase stability in the rocket, the centre of pressure and centre of mass should be in specific positions on the rocket. The centre of mass is to put simply, a balance point in an object. It is a uniform gravity field that averages the external forces surrounding the object to equalise the forces acting upon it, such as a balance point on a see-saw (HyperPhysics, 2000). The centre of pressure on a rocket is the average location of the pressure, which varies around the surface of an object (NASA, 2010). The fins and aspects of the rocket all contribute to the end position of the centre of mass and pressure and so the centre of mass should be as close to the middle as possible, with also the centre of pressure towards the back of the rocket, which is achieved by the use of big fins or fins that add weight to the rear of the rocket. When constructing the rockets, there are things to consider: Newtons First Law: - Objects at rest will stay at rest, or objects in motion will stay in motion unless acted upon by an unbalanced force. When the rocket is sitting in the launcher, the forces are balanced because the surface of the launched pushes the rocket up while the force of gravity forces it down. When the water rocket is pressurised, the forces become unbalanced and thrust will provide upward direction for the rocket to follow. Newtons Second Law: - The acceleration of an object is directly related to the force exerted on the object and oppositely related to the mass of that object. The acceleration of the rocket will depend on how much thrust and force is put behind the upward strength to aid the rocket. Newtons Third Law: - For every action, there is always an opposite and equal reaction. When the rocket launched, there will be air drag and gravity pulling against the rocket, along with the upward thrust provided. Considering the design of the bottle rocket, fins play a major role in steadying and effectively pushing the rocket to increase the rockets aerodynamics. If the fins are too far forward on the rocket it could put off the centre of mass and therefor cause the rocket to become heavily unstable. Some general tips for the fin design are that they should be thin or tapered, angled backwards and with rounded corners rather than sharp corners (Williams, 2014). This experiment is being conducted to explore the diverse variables involved with the rockets and how they function, and to analyse and explore further investigations included in the subject of the physics field that contributed to the understanding of the rockets. Aim

The aim of this task is to research the key principles of rocket design and stability needed to develop the rockets. It is to observe the effects a range of variables has on the water rocket...

Bibliography: HyperPhysics, 2000. Center of Mass. [Online]
Available at: http://hyperphysics.phy-astr.gsu.edu/hbase/cm.html
Moore, S., 2014. Design Consideration for Water Bottle Rockets. In: S. Moore, ed. Water Bottle Rockets. Gold Coast: Helensvale, p. 1.
NASA, 2010. Center of Pressure. [Online]
Available at: https://www.grc.nasa.gov/www/k-12/airplane/cp.html
Williams, A., 2014. Bottle Rocket Design. In: A. Williams, ed. Class Notes. Gold Coast: Helensvale, p. 2.