#GOALS: IWBAT...
1. Define the components of the acceleration equation
2. Solve an acceleration problem using the GUESS method
WARM-UP:
Review the image of the rock falling from the cliff (LINK)
Is the rock moving at a constant velocity?
How can you tell?
What does the text call this 'falling without resistance?'
Copy the Two Rules for Free-Fall:
CLASSWORK
Lab 3 Work time (25min)
complete the Q & A
Acceleration Notes (10 min)
Go to page two (LINK). Answer the following in your notes
what is the magnitude of g? direction?
Find and record the value of g here in LA, and for Barrow, AK.
Are they the same g? Why/why not? (hint: LINK)
Copy the equation for acceleration
What is the pattern for change in velocity shown in the Time / Velocity chart
How do we solve acceleration problems? (15 min)
Solve the problem along with Mr. P and myself.
HOMEWORK (due next class)
Read #013A: Lab 3 - Acceleration of a Penny LINK
#012A: Watch the following video on acceleration problem solving (LINK). Take notes & answer the EdPuzzle questions. Post a photo of your notes and answers to the GC
#012B: Solve CH 2 pg 53: #51, 52, 53, 57 and CH 3 pg 61 #4 using the GUESS procedure. Post a photo of your notes and answers to the GC
09/09/16
WARM-UP:
Constant Velocity
Open CH2 of the textbook to Page 38, and look at figure 2-12 in the bottom right corner of the page.
Show your work - don't write the questions
1. What is the position (m) of the runner at Time 0 (zero)?
2. What is the position (m) of the runner at Time 1 (1 sec)?
3. What is the difference in position (m) between those two times?
4. Calculate the velocity of the runner between T(0) and T(1).
5. Repeat steps 1-4 between T(2) and T(6). Find the velocity during that time period.
6. Read the classwork if you finish early
CLASSWORK:
1. Goals for You as Students:
- I want you to leave this class everyday feeling confident, feeling like you are more able to figure out how to solve Physics problems than when you walked in.
- You are all super smart, otherwise you wouldn't make it into this class
- Ownership for learning:
- it's on you, me, and to a lesser extent, your parents, family, and even friends
- Your responsibility: Homework
- Videos and reading are your intro to content
- Your job to absorb as much as you can
- What does it look like to learn on your own from a physics video?
- How do you know that you've learned something?
- Go to the link, and answer the two questions. Put your name at the end of your answer --> LINK
1. A General Procedure for Problem Solving: "GUESSing"
Once a physicist has used a graph to prove a relationship between two variables, that relationship can then be used to understand all future interactions between those same variables.
For instance, we used a graph of position vs time for an object moving with constant velocity to prove that
v = Δx/Δt. This occurred no matter how fast the object moved. Therefore, we can use this equation for any future situations in which an object is moving with constant velocity.
Consider the following situation. Mr Alexander wants to fly from KVNY (Van Nuys Airport) to KTVL (South Lake Tahoe Airport) for his high school reunion. The reunion is at the airport, and starts at 5:00pm on Saturday. Mr. Alexander's Flight Plan (<-- click the link) shows the distance from Van Nuys to Tahoe. The Cessna 172 that Mr. Alexander rents averages a speed of 115 miles per hour on a clear day with no winds - today the winds are calm and are no factor. At what time should he leave if he wants to reach South Lake Tahoe in time for the reunion?
There is a process we can use when solving math problems like this one called GUESS. GUESS is an acronym that helps organize our problem solving. Here is what it stands for.
Givens: A given is any number written in the problem. Numbers include attached units.
Unknowns: An unknown is the number or numbers that the problem is asking us to calculate.
Equations: An equation is the algebraic representation of the relationship between the variables in the problem. Some problems may require multiple equations to solve.
Substitute: Once the equation has been identified, the givens are substituted in for the variables. Leave the unknown as a variable.
Solve: Use math to isolate all the non variables to one side of the equality and the unknown to the other side.
Let's apply this process to the problem of Mr Alexander's journey to South Lake Tahoe.
G Δx = 289.9mi tf = 5pm v = 115 mi/hr
U departure time - how long the flight takes (Δt)
E
S
S
Practice the GUESS procedure on problems 49-51 from page 53 in chapter 2 of the textbook. (10min)
2. Velocity Inquiry Lab Prep
TITLE: Constant Velocity
Your team will design an experiment to compare the position of an object moving with constant velocity over a series of time intervals. Discuss with your group the variables that will need to be measured to prove that an object is moving with constant velocity. Decide which variable being measured will be dependent and which will be independent.
Measurement Equipment
You will have access to several pieces of lab equipment. There are ball bearings, ramps, meter sticks, rulers, etc. You may use objects from home if you like. Make a list of all the equipment you expect to use. You are allowed to make changes during the lab.
Discuss with your group how you could take the proper measurements to prove that your object is moving with constant velocity. Put together a list of procedures that you will follow. Perform at least three trials.
Graphing
After you take your measurements, construct a graph of your data and draw a best fit line. Use Google Sheets via your school Google account, and share your graph with me Construct one graph for each set of data that you take. Calculate the slope of the best fit line.
Percent Error
When you have calculated the slopes, take an average of the three values measured without the phone. Also take an average of the three values measured with the cell phone. Now compare the average value with the value that is farthest from the average. You can calculate your percent error as follows:
percent error = (average - outlier) x 100
average
For all scientific experiments we aim for a % error that is less than 5 and preferable less than 1. The smaller the better. How did your team do? Answer the following questions.
What sources of error did you identify during your experiment?
How many sources of error were sources that your team had control over?
For each of the sources of error you identified above, suggest a possible way to change the experiment to minimize that source of error.
Lab Report
http://www.chem.ucla.edu/~gchemlab/labnotebook_web.htm
Introduction
Materials: List all the materials used in your experiment.
Procedure: List all steps that your group followed in this experiment. Include diagrams of your experimental setup. Your procedure should be detailed enough that another group could follow your steps and get the same conclusions.
Data: Data should be listed in data tables. There should be one data table for each trial.
Analysis: Graph your data. There should be one graph per data table. Calculate the slope for each graph. Take a mathematical average for the slopes. Use the average slope to write an equation that for the line. Calculate the percent error for your data. Answer the analysis questions.
What sources of error did you identify during your experiment?
How many sources of error were sources that your team had control over?
For each of the sources of error you identified in problem two, suggest a possible way to change the experiment to minimize that source of error.
Conclusion: Answer the following conclusion questions.
What is the relationship between x and t for constant v?
Were you able to achieve constant velocity? How can you tell?
Homework:
Practice! 52-54 from page 53
Homework (due Wed): Pg 53, prob 59
WARM-UP:
A truck is traveling at 48km/h. How many hours would it take to travel 72km? Use the G.U.E.S.S. procedure to solve.
Direct Measurement Quiz
Mr Alexander will be showing a video of an object in motion. You will take position and time data and use them to calculate the velocity of the object.
Classwork/Homework Review
Constant Acceleration Lab
Your team will design an experiment to measure the relationship between distance and time for an object with a constant acceleration. Read the beginning of CH 3 (pg 56-59. Look at the figures, Launch Lab, and Mini Lab while you're reading. Then discuss with your team the experimental setup you will use and the assumptions you will need to make.
Materials
You will have access to the 50 gauge ball bearings, AA batteries, and pennies. You will also have access to the wood ramps, rulers, any of your personal stuff, and the things on your desk. Make an equipment list based on your experimental design. You must also choose which data collection method you wish to use for this lab experiment, eyes or camera.
By the end of the period, you should have the following in draft form:
Abstract
Materials
Procedure with list of assumptions