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Designing ExperimentsScientists test their hypothesis by keeping track of the variables (things that change) throughout the experiment. When possible, only one variable is changed at a time while the others are controlled. Consider this example:A researcher wants to know if adding nitrogen to the soil will make grass grow taller. They take two plots of land that receive the same amount of sun, same amount of water and have the same type of soil. One plot is left alone to grow naturally while the other has nitrogen added. This is a controlled experiment.(here are some terms you will want to know)Controlled experiment- an experiment where only one variable is changedControl group- part of the experiment where nothing is altered (used to compare the experimental group’s results)Experimental group- part of the experiment where one variable is alteredIndependent variable- what is changed in the experimentDependent variable- what is being affected by the independent variableTo help you understand these terms, consider my earlier example:The control group is the plot of grass where nothing is changed. The experimental group is the plot of grass with the nitrogen addedThe independent variable is adding the nitrogenThe dependent variable is the length of the grassThe next page has three experiments explained. Your job is to identify the independent variable, the dependent variable and the control. This is for you to practice; it will not be graded.1. A student wanted to test how the mass of a paper airplane affected the distance it would fly. Paper clips were added before each test flight. As each paper clip was added, the plane was tested to determine how far it would fly. Independent variable ___________________________ Dependent variable ____________________________ Control _____________________________ 2. Two groups of students were tested to compare their speed working math problems. Each group was given the same problems. One group used calculators and the other group computed without calculators. Independent variable ___________________________Dependent variable ____________________________ Control _____________________________ There can be several controlled variables. If an experiment is to be useful, only one variable at a time can be manipulated intentionally. All other variables must be controlled throughout all parts of the experiment. If more than one variable is altered (changed), the results of an experiment cannot be interpreted with any validity. 3. An experiment was performed to determine how the amount of coffee grounds could affect the taste of coffee. The same kind of coffee, the same percolator, the same amount and type of water, the same perking time, and the same electrical sources were used. Independent variable ___________________________ Dependent variable ____________________________ Constants (3) _______________________________________________________________This needs to go in your lab book following the same format we used for the oreo lab. The procedures for the lab are found on the following page. The instructions may be confusing so take your time, read the instructions a couple times and look at the diagram, it will help you understand what to cut and what to fold. Your first helicopter will use the dimensions in Option 1. From there, you can change one thing at a time until you have constructed the ideal helicopter. If after reading the instructions multiple times and it doesn’t make any sense, then ignore the paper, and get back to recovering, you can make up the lab when you come back to school.Helicopter LabPurpose: To display our understanding of experimental design by building the best paper helicopter possible. * “Best” is determined by the length of time the helicopter stays in the air. Important Notes:There is a list of options for you to choose from. There is a total of 12 possible constructs, you need to get at least eight of them built, tested and recorded. This is a controlled experiment, which means only one variable will be changed at a time.To ensure that only one variable is changed at a time, whoever cuts the first helicopter must make all the cuts, whoever drops the helicopter must drop the helicopter every time, whoever times the drop must time the drop…get the point?HelicopterRotor LengthLeg LengthLeg WidthPaperclipTime12345678Data:Analysis:What were the dimensions of the helicopter that lasted in the air the longest?Which aspects of this experiment were controlled? Identify the variables:Discussion: Did you have any issues with this lab? Conclusion: What did you discover? (best dimensions; understanding controls/variables)Helicopter LabHelicopter DimensionsOption 1Option 2Rotor Length7.5 cm8.5 cmLeg Length7.5 cm12.0 cmLeg Width2 cm5 cmPaperclip on LegNoYes3480435133350Directions:***Pro Tip: Make all measurements and marks before you begin cutting***Cut paper to a width of 5 cmCut length of paper using following formula:L=length of leg+length of rotor+2 cmCut the dotted lines at Leg A and Leg C. The length of each cut is:L = (5 cm – leg width)/2Fold Leg A onto Leg B and Leg C onto Leg BCut rotors along dotted lines to appropriate length.Fold Rotor A and Rotor B in opposite directionsIf applicable, add a paperclip to the bottom of leg.Test:Drop helicopter from a height of 2 metersRecord amount of time it takes to hit the floorTry multiple variations of helicopter until you have determined which combination lasts in the air the longest.00Directions:***Pro Tip: Make all measurements and marks before you begin cutting***Cut paper to a width of 5 cmCut length of paper using following formula:L=length of leg+length of rotor+2 cmCut the dotted lines at Leg A and Leg C. The length of each cut is:L = (5 cm – leg width)/2Fold Leg A onto Leg B and Leg C onto Leg BCut rotors along dotted lines to appropriate length.Fold Rotor A and Rotor B in opposite directionsIf applicable, add a paperclip to the bottom of leg.Test:Drop helicopter from a height of 2 metersRecord amount of time it takes to hit the floorTry multiple variations of helicopter until you have determined which combination lasts in the air the longest. ................
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