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CP PHYSICS!Good morning! Please…• Take out your homework to be checkedUse the graphs shown toanswer the warm-up question:1. Calculate acceleration from the v vs. t graph shown for t = 0-4 seconds.2. Develop an x as a function of t equation for t = 7-15 seconds(use equation xf = xi + vit + ½ at2) 1.
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HOUSEKEEPING!• ***LAST DAY TO MAKE UP WORK, HAND IN LATE WORK IS 10/26***• Word Wall!• Catapults coming soon! Launching is on 10/26 • Rules/grading are posted online • Due today: • A status update on your progress • Your plans for how you will construct & test your catapult• Coming up… • Formal lab report will be due Monday 10/24 • Quiz will be Monday 10/24• There will be a unit 2 test on 10/31
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WORD WALLPeriod 2 Period 6• Wendy - physics • Hunter – dependent variable• Doug – free-fall • Kaniz – independent variable• Dylan – acceleration due to • Ethenne - hypothesis gravity • Alejandra – controlled• Calyah – dependent variable experiment• JJ – independent variable • Jimmy – scientific method• Karol – hypothesis• CatieSome words are in the book…others are not…you may have to google it to get all the information you need
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HOMEWORK SOLUTIONSPg. 72 # 34-36, 38, 3934. Ball thrown vertically upward. What happens to the ball’s velocity… (a) … while it is in the air?decreases as it goes up, increases as it goes down (b) … at maximum altitude? It is zero What is the ball’s acceleration… (c) … when it reaches its maximum altitude? It is -9.81m/s2 (d) … Just before it hits the ground? It is -9.81m/s2 (e) does its acceleration increase, decrease, or stay constant? It stays the same35. The velocity of the solid ball (left side) is greater, and so is itsacceleration.36. Accelerations of the two pins are both the same, even if one is going upand the other is going down!38. 39.6 m/s39. t=3.9 sec
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• In this lab, we will use a dot timer to calculate gravity in two ways G WHIZ LAB • Graphically - but how? Yf = yi + vit + 0.5at2 • Using equations: Which can be simplified to… • What equation can you use to calculate gravity if given: Yf = 0 + 0 + 0.5at2 • Yi = 0 m • Yf = gathered data Yf = 0.5at2 • Vi = 0 m/s • Vf = ? • a = ? (what we are solving for) • t = gathered data
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G WHIZ LAB On “ticker tape computer graphing”Lab Instructions instructions…• Answer questions 1,3,4,5 • Change all references to “Time (1/60 sec)” to “Time (1/30 sec)”• On back… • In table headers and in • For your analysis, you will instructions measure the distance between every other dot • When generating the velocity calculation… • Last sentence of paragraph 2… • In instructions… • “each time interval is • In cell I4, type =C4*30 1/30th of a second”… instead of =C4*60
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FORMAL LAB REPORT WRITE-UP• Lab report should be in paragraph form, broken up into sections as required• Sections to include (which are listed on rubric) • Problem definition • What question(s) are you trying to answer? • Include any preliminary observations or background information about the subject • Experimental design • Data presentation • Conclusion & discussion
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PROBLEM DEFINITION• Statement of the problem• Hypothesis • What do you think the value of acceleration will be? • Do you think the number of washers (or the mass) attached at the end will make a difference in the value of acceleration? Why or why not?• Identify Independent variable: the variable we are in control of changing• Identify dependent variable: the variable we are measuring – its results “depend on how the experiment goes”
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EXPERIMENTAL DESIGN• What materials are used in this lab?• What safety notes need to be considered?• How many trials were done?• Were there any constants? Was there a control?• Explain the procedure in enough detail so that someone could repeat the experiment
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Data Time (1/60 sec) 1 Distance (mm) 2 Presentation 2 3 1.5 1.5 Distance (cm) vs. Time Graph 4 2 250• Clear data tables with 5 2.5 6 3 200 title, labels and units 7 3.5 Distance (cm) 8 4 150• Sample calculations 9 3 included 10 3 100 11 3.5 50• Equations used are provided 0 0 50 100 15 Time (1/60 seconds)• Graphs with title, labels, and units Velocity vs. Time Graph for Ticker Tape 200 • Dependent variable is Lab 180 y = 1.312x always on the y 160 R² = 0.936 axis, dependent variable 140 Velocity (cm/sec) is on the x axis 120 100 80 60 40 20 0 0 20 40 60 80 100 120 140 160 Time (1/60 seconds)
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CONCLUSION AND DISCUSSION• Lab questions are answered Lab questions: sufficiently 1. Was there a difference between the accelerations for the different masses? • Answered in a way so that Explain why this may occur. the reader does not have to 2. What is the acceleration of gravity on the know the question being moon? Why is it different than on the Earth? asked when reading your response. 3. Did your graphs show a constant acceleration? Explain. 4. Calculate and explain what is represented by the area under your velocity vs. time graph. 5. Would you expect your calculated values for acceleration to be higher than, equal to, or less than the accepted value for accelerated due to gravity (9.8 m/s 2)? Why? Calculate the relative error. Relative Error = your result– accepted value (9.80) x100 accepted value (9.80)
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CONCLUSION AND DISCUSSION• The lab conclusion is discussed • What effect did the independent variable have on the dependent variable? • Support your conclusion by referring to at least two references to graphs and tables to show reader how you reached your conclusion • Validity of experiment is discussed: • Was there anything that you noticed while performing the lab which could have affected your data? • Were the number of trials adequate? • Compare your results to your hypothesis – were the results what you thought they would be? Why or why not?• Possible sources of error are identified & suggestions are made to reduce error• Ideas for improvement and extension are provided.• Wrap up conclusion, make connections to everyday situations.
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