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Inquiry: Inertial Balance

Purpose: To learn how to use spreadsheets to determine linear relationships between variables and thus prove physics equations.


Connect the photo gate to the USB port on the laptop, launch Data Studio and choose the Pendulum and Photogate timer. You may have to select New Activity under the File menu before you do this. Under Setup/Constants enter the width of the pendulum as 0.01 m. Attach a lab mass to the pan and pull slightly to the side and release. Click start on the computer program until it has recorded around ten readings and then click stop. Highlight 3-4 of the records in the middle. Click on the stats (Σ) button to get the average value of the readings and record. Using 20.0 gram increments measure the periods of the masses up to 300.0 grams. Determine the period of the wheel as well.

Inquiry Questions:

  1. Determine the mathematical relationship between Period (T) and Mass (m) for the classroom inertial balance.

  2. Use the equation to create a quick program to determine the mass if given a period. Check for the wheel.

  3. If the equation for the period of an inertial balance is given as the following where m is the mass and T is the period, calculate a numerical value for k, which is the spring (elasticity) constant for our balance. Just ignore the y-intercept value in your equation from question 1.

  4. A seconds-pendulum is an inertial balance that takes 1 second to swing one way and another second to swing back. What is the elasticity constant k of a 1.0 kg mass on a seconds-pendulum?

  5. Gravity is measured at various locations from the center of Earth as seen in the following table. Using a spreadsheet, graph this data and then determine the mathematical physics equation that relates these two variables. Keep manipulating the data and re-graphing until you have an R2 value of 1. (Use the spreadsheet to convert your distances to meters)

Distance (km)

Gravity (m/s2)