# Activities

• • • ##### Subject Area

• Math: Algebra I: Linear Functions

• ##### Author 9-12

60 Minutes

• ##### Device
• TI-73 Explorer™
• TI-83 Plus Family
• TI-84 Plus
• TI-84 Plus Silver Edition
• TI-Navigator™
• ##### Software

TI InterActive!™

• ##### Accessories

CBL™/CBL 2™
CBR™/CBR 2™
TI Connectivity Cable

## Tight Rope

#### Activity Overview

In this activity, students examine quantities that are linearly related and can be visually represented using a straight-line graph. Students collect distance versus time data using a motion detector and find a model for the time-distance data set.

#### Before the Activity

• Connect the computer to the CBL 2™ using the TI connectivity cable

• Connect CBR 2™ to the DIG/SONIC port of the CBL 2™ unit and set it up to take readings

• Open a new TI InterActive!™ document
• See the attached PDF file for detailed instructions for this activity
• Print pages 8 - 13 from the attached PDF file for your class

• If you plan to use the EDC quiz as a follow-up, download the file and have it ready to distribute to students via TI-Navigator™.

#### During the Activity

Distribute the pages to the class.

• Place the motion detector on the table and collect distance versus time data as the student walks away from the unit
• Plot a graph of distance versus time
• Observe that the graph is linear
• Find b (y-intercept) when x = 0 on the graph
• Find the slope of the line by guess-and-check method until the slope value models the data well
• Use values of b and m to form a linear equation of the line in the y = mx + b form
• Identify two points and calculate the slope using the formula m = (y2 - y1)/(x2 - x1)
• Compare the slope found earlier with the guess-and-check method and the calculated method
• Use the linear regression function to get a line that best fits the data and record the linear equation y = ax + b and values of a and b
• Compare the values of the slope and y-intercept from the linear regression model with the values found experimentally
• Observe that the linear regression equation is a better fit
• #### After the Activity

Students complete the analysis and answer questions.
If you are using the TI-Navigator System with the TI-73 you will need the attached .pdf file.
Review student results:

• As a class, discuss questions that appeared to be more challenging
• Re-teach concepts as necessary