Rocket Investigation D. Crowley, 2009

Rocket Investigation Your task is to investigate what affects the maximum altitude a water rocket can reach As you complete this experiment you need to think how you can make this test a fair one, how you can be accurate and precise, and how you can ensure the results are reliable Wednesday, May 13, 2015

Initial Questions Initially you need to brainstorm what we need to achieve the greatest altitude for our rocket?  How is the rocket powered – what is the optimum amount?  What will limit our rocket’s maximum height?  What will you construct your water rocket from?  How will stability affect the rocket?  How will aerodynamics increase the performance?  How can we measure our height? A simple rocket can be built of an empty plastic bottle… Partly filled with water and pressurised air the rocket can be blasted high up in the air – the pressurised air expels the water, which in turn creates the thrust to accelerate the rocket The thrust is counteracted by the air resistance and the weight of the rocket

Initial Questions Thrust is achieved by the pressurised air forcing the water to expel – the proportion of air to water is crucial to the thrust that will be achieved Newton's third law explains the rocket's forward propulsion – as the water is expelled is pushes in one direction (downwards) This has an equal and opposite effect on the rocket, pushing it up with an equal force The greater the force the water can be pushed out with, the greater upward force the rocket will experience

Initial Questions Stability is crucial for our rocket, so fins will help it fly in a straight line Aerodynamics are also crucial – the lighter the weight and the more aerodynamic the vehicle is the higher it will go – air resistance needs to be kept to a minimum! Height can be suggested by the time the rocket was airborne (i.e. a rocket which has ‘flown’ for a longer time has probably been higher, however this is a basic assumption) Height can be more accurately estimated using trigonometry…

Rocket Altitude How can we measure the altitude (height) reached by our water rocket? The easiest way to measure the altitude is to use trigonometry…  Launch the rocket with someone a known distance (d) to the side of it  Point at the rocket as it launches and stop where the rocket reached it’s maximum height – estimate the angle of the pointed arm from the ground (straight up would be 90 o ) – a protractor may help!  Now multiply the distance by the “tan” of the angle

Rocket Altitude E.g. if the distance was 20m and the angle was 60 o (20 meters)*tan(60 degrees) = 35m Distance (d) Angle of highest point ( o ) 0O0O 90 O

Initial Experiment Watch the demo of the water rocket – consider what variables are affecting the launch, and what can be changed to alter the altitude the rocket reaches Consider the design of the rocket – what will you modify when you make your own rocket and for what reason?

Key Words During your investigation you will come across some key words: -  Accurate: a measurement that is close to the true value (accuracy can be increased by controlling the key variables)  Precision: this is a more precise measurement, which can be achieved by using a smaller scale  Reliability: the experiment needs to be repeatable – if someone else did the experiment then they should get exactly the same results: this comes from repeating your experiment  Dependent variable – what is changed by the experiment (what you are going to measure)  Independent variable – what you change  Control variable(s) – what you are going to keep the same, making the experiment more accurate

Introduction Initially write you introduction for the rocket investigation Note your aim (what we are doing); why we are doing it and what tests which will carry out and why I.e.  What affects the potential height of our rocket (what powers it and what slows it down)?  What other design features will your rocket have (a design may help here)  Explain why the rocket goes up (hopefully)!  What is it you are going to measure and how?

Method Your task is to now consider what methods you are going to use to measure the height of your rocket and what factors affect the altitude reached How are you going to make your experiment: -  Accurate (as close to the true value as possible) – e.g. height, water amount…  Reliable (so someone else can repeat this experiment and get similar results)  Precise (how many readings are going to be taken and how can you ensure each repeat is completed in the same way) Complete a step-by-step guide to completing your experiment Note your independent variable (thing you change) and how you will change this Note your dependent variable(s), and how you will measure this What data are you collecting / recording

Method When you have designed and constructed your rocket you will be able to change the amount of water carried by the rocket – all other aspects must remain consistent Once you have measured an exact amount of water you can launch it and estimate the maximum height reached Record the heights reached when using different quantities of water (record the amount too)!

Prediction What do you expect will happen when you change the independent variable Can you explain what will happen, and why you think this E.g. I think that when I change the… the… will… because… We should find there is a specific quantity of water that allows a maximum altitude – there is a trade off specific to each rocket: we need enough water to expel to act as propulsion, but we also need enough air to pressurise to push the water out… More water also equals more weight – again each rocket with have its own optimum amount to carry

Apparatus Order Form Finally, you will need to order all the apparatus your require to carry out this experiment Ensure you have thought of everything, and just as importantly you must identify how much equipment you need – e.g. 2 sheets of cardboard; specific measuring equipment for water (the bottle will be 2 litres in size) Your apparatus form must be signed off before it will be given to the laboratory technicians

Results Produce a results table for the experiment (when the quantities of water are changed) Remember to include your units and how many repetitions you will be doing

Results - Altitude Quantity of water (cm 3 ) Estimated rocket altitude (m) 123Average etc…

Experiment You have this lesson and the next to complete your experiments Any damage to your rocket will need to be repaired outside – remember to make this repair as close to the original design as possible Remember to be as accurate and precise as possible, repeating an appropriate amount of times and recording your results You will also need to calculate all the averages this lesson for your results

Conclusion Your task is to graph your results of altitude against water volume A scatter graph is most suitable – volume of water on the x axis (cm 3 ), and altitude reached (m) on the y axis Remember to add a title; units etc… Once you have drawn your graphs you need to complete an analysis – what do the results show you / why do you think this is?

Graph

Evaluation Finally you need to complete an evaluation – were there any anomalous results? What errors may have caused these: -  Random error (happens occasionally)  Systematic error (same mistake occurred every time (likely due to you measuring this incorrectly) How accurate was your experiment – did you consistently get the same results? Was your method fair allowing you to collect accurate results? Do you have enough reliable evidence to support the conclusion that you have made What improvements would you do if you could repeat this experiment?

Water Rocket You can visit the NASA water rocket page (click here)click here The NASA page also consists of a rocket game (click here)click here