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Title: Constant Velocity Lab
Principle(s) Investigated: Students will be able to state the meaning of constant velocity verbally, mathematically, and graphically.
Standards : HSN-Q.A.3- Choose a level of accuracy appropriate to limitations on measurement when reporting quantities
SL.9-10.1b- Work with peers to set rules for collegial discussions and decision-making
RST. 9-10.3- Follow precisely a complex multistep procedure when carrying out experiments, taking measurements, or performing technical tasks, attending to special cases or exceptions defined in the text.
RST.9-10.7- Translate quantitative or technical information expressed in words in a text into visual form (e.g., a table or chart) and translate information expressed visually or mathematically (e.g., in an equation) into words.
Materials:
- 1 velocity car ( for each group)
- Small pieces of masking tape (for each group) & a starting line tape
- 1 Stop watch (for each group)
- 1 meter stick (for each group)
Procedure:
Data Collection: https://docs.google.com/spreadsheets/d/1r1SQmjfmyHeCEM40XiBqzvdBuNBrIpvAu91hAhDuiPY/edit#gid=0
How does mass affect acceleration and/or velocity?
What are the forces acting upon a car on an incline?
Why does the car move forward from an incline?
Flat surface verses incline?
In this lab, I assign students by the numbers on their tables (seat #1-4 at each table) to have jobs during the lab. The jobs are: (1) Car Controller (2) Data Collector (3) Time Reader and (4) Data Recorder. The Car Controller is in charge of starting the car at the beginning of each trial in the same location each time. The Data Collector walk alongside the car and records the position at each designated instant of time. The Time Reader states the pre-designated time intervals so the Data Collector knows when to record data. The Data Recorder is in charge of inputting data.
Before students start the lab, I tell them to make sure to collect at least 6 data points per trial, which requires them to have 6 pre-designated time instances. I prompt students to choose their time intervals that they would like to record whether it is 0.5 seconds or 1 second or even 2 seconds. I ask the Data Recorder to enter the points that their group have chose. After they have chose their times (independent variable), I tell them that it is important to average our dependent variable (position) data instead of taking just one trial. So instead of just 1 trial, students should average the results from 3 trials. When they graph I ask them to plot the time and average of the position at time instance. The last thing I mention to students is that they must choose a starting position. I try to have groups choose different starting points other than 0 meters so that we can identify the y-intercept as initial position later on. Once I tell students these things I allow them to choose any point in the room or hallway to set up with their dune buggy and meter tape.
Student prior knowledge:
The goal for this lesson is for students to observe and develop a model for constant velocity motion using constant velocity carts that I call dune buggies. I start out the unit with a lab so that we can develop the graphical, written and mathematical models from a experience of constant velocity motion with the dune buggies. Students start out the lab by asking questions about a situation that they observe. Then they develop an investigation and produce a model from the data that they collect that we discuss as a class.
Explanation: When students are completed with their data collection, I have them create a graph of their data. I will have students complete the lab summary as a group so they have all of the information submitted to me as a group before the students discuss it as a class. The lab summary includes their mathematical, graphical and written representation of their data. I do the lab summary so students have a chance to analyze their data prior to the whiteboard session. I like for students to have everything they need with respect to the data during the whiteboard session so I have them complete the lab summary first
Questions & Answers:
Questions to lead the discussion:
- Experimental Procedure- I ask students these questions to refer back to where we started and to give the discussion some context.
- What was your independent variable? Dependent variable?
- What does it mean that we controlled variables?
- How did you control your variables?
- How do you know if you collected enough data?
- Graph Analysis Questions-When I ask these questions, I ask students to look at many groups data and compare it to their own data before answering the questions.
- What do we see in common with all of our graphs? (focus on axis labels, units, variables in the right place, etc.)
- What does the straight-line graph tell you about the car’s motion?
- What does the slope mean in terms of this experiment? (For every statement…)
- Why do different groups have different values for their slopes?
- What would a larger slope look like if it were added to your board?
- What does the y-intercept mean in terms of the car’s motion?
- What is the story of this graph?
Applications to Everyday Life:
When we decide that position and time are the variables, I then ask my students which should be the independent variable and which should be the dependent variable. They should come up with time as the independent variable and position as the dependent variable. In this lab, either measurement could be independent, but since in physics the convention on position vs. time graphs is to have time on the x-axis, I want to follow that.
Photographs:
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