- Ask your instructor for the Class Key for your class.
- If you don't have an account on Pivot Interactives, go to www.pivotinteractives.com and then to Join a Class. Enter the Class Key provided by your instructor, an email address, and a password to create an account and select Create Account.
- If you already have a Pivot Interactives account, log in, and then click on your name in the top right, and select Join Class from the list.
- Enter the Class Key provided by your instructor and select Join a Class.
Note: In your future visits you'll be able to "Log In" directly with your email address and password.
- Select My Classes
- Find the activity that you'd like to complete
- Open the activity by selecting View
These instructions refer to the Hill Runner (Jessie Diggins). If your instructor has assigned that activity open it up and follow along. If your instructor hasn't assigned it, ask them to assign it, or simply open another activity, but be aware that each activity has a different set of features.
- Read the instructions for the activity
- Select the ⓘ in the upper left of the video player frame to find information and hints about the video:
Click the "i" in the upper right of the video player to learn about the controls.
- You can find the interactive tools needed to analyze a video by selecting the tool icon in the upper-right of the video frame. In the Hill Runner activity shown below, there are three tools: a stopwatch, a ruler, and a protractor.
- Clicking the ruler icon places this tool in the video frame.
- The ruler can be moved by clicking and dragging. Some rulers can be rotated by clicking on the round dots on the sides of the tool, and dragging to rotate.
- Many of our videos allow the user to change parameters in the video. In the activity below, the user select whether Olympic gold medalist Jessie Diggins carries a backpack or not.
- The Hill Runner activity lets users select between real time (30 frames/sec) and 8x slow-motion.
- This activity also gives users access to successive trials under the same initial conditions.
- Be sure to hit GO. The new video won't load until GO is selected.
- Whenever you use a data table remember to label the columns with the quantity in the top row (displacement, time, etc) and with the units below (meter, seconds, etc).
- Enter your data
- To add more columns select the more options icon
- Select Insert Column Right
- At this point you can either enter more data manually, or if you want the table to automatically perform a calculation select Change Column formula
- to calculate average velocity select "Displacement"...
- ....divided by....
- The new column will self populate when you hit Go
- Select the quantity you would like to have on the horizontal axis.
- Select the quantity you'd like to have on the vertical axis
- If you'd like to fit your data to a straight line select Linear Regression
- If you have fit your data to a straight line, the equation for the best fit line will appear here.
- The r-value indicates how well the line matches the data. A value of 1 indicates a perfect fit.
A video explaining this process is available here.
- For this method it's important to collect data at uniform intervals of time. In the screenshot below I have collected data every second. Note: If data is not collected at uniform intervals of time then some time segments will be over represented in the velocity vs time graph and others will be underrepresented.
- Place Displacement (or position) on the vertical axis and time on the horizontal axis.
- Activate the Linear Regression
- to 6. By clicking on a data point you can remove it from the linear fit. Remove all of the points except for the first three. When a point is removed from the fit it will turn into a gray **x** instead of a pink dot.
- The resulting slope will represent the average speed over the interval selected (in the image below from t=0-2s). We'll use this slope (6 m/s) to represent the instantaneous velocity in the center of this time interval (ie at 1 second).
- Create a new column on the right using the More Options icon
- Give your new column a name (Instantanous Velocity) and units (m/s).
- This method of determining the velocity does not allow us to determine the velocity of the first or last points, so will leave the first data row in this column blank.
- We used the steps above to determine the velocity at 1 second. It's 6 m/s according to the slope of the graph above so we'll enter 6 in this spot.
- In order to select or deselect point to include in the linear fit we can either click on the points directly on the graph (as outlined above) or we can include all of the points in the curve fit by selecting this check-box.
- Use these check boxes to change which points are included in the fit.
- In order to determine the instantaneous velocity at 2 seconds we'll want to fit a line to the three points centered at 2 seconds. That means we'll deselect for first (leftmost point). Points can be deselected by clicking on them directly or by deselecting them using the corresponding check box in the table (see instructions above).
- Then we'll want to click the next point to include it in the linear fit.
- The slope of those three points represents the instantaneous velocity of the center point (at 2 seconds). In this case the slope is 12 m/s which we'll enter into the table as the instantaneous velocity at 2 s.
We'll continue the process until we have found the instantaneous velocity of all the points (except for the first and the last). Then we can create a velocity vs time graph by selecting "instantaneous velocity for the Vertical axis and time for the horizontal axis. The slope of the new velocity vs. time graph will represent the acceleration of the object.
Your work is automatically saved as you go. At the bottom of each activity are Save and Save and Close buttons. You can press these to save your work, but your work will be automatically saved even if you don't.
After your instructor has reviewed your work on an activity, you can find their feedback by...
- Selecting My Classes
- Finding the activity
- Selecting View will open the activity with your work along with any scores or comments your instructor has provided.
Note: often instructors will not review all of the parts of an activity but rather will select a few key elements to review. Thus if you received zero score for some questions it doesn't necessarily mean that your work was incorrect, rather it could be that those questions were simply not reviewed by your instructor. For this reason it's important to pay attention to the written comments provided by your instructor and not only to the numerical score.