iLab at Iona Prep

The purpose of this lab is to measure the gravitational constant "G". (Revised 12.18.20)

In the right frame you have a simulation of two masses. You may adjust the distance between their centers, and you may also adjust the magnitude of each mass.

Newton put forward that the gravitational force of attraction between any two masses would be directly proportional to the product of the masses and inversely proportional to the square of the distance between them. The equation would look like this:

F = G * m1 * m2/ r^2

In this lab you will measure the force (F), the masses (m1,m2) and the distance between them (r) and from those the spreadsheet will calculate the value of the Universal Gravitational Constant, G.

- First notice that the force on m1 by m2 and the force on m2 by m1 are equal, but that the numbers are ridiculously small and even hard to read. In the Force Values box, click on Scientific Notation. That makes the numbers easier to read and copy.
- Open the Google Sheet and note the variables which you will be measuring (m1, m2, r, F) are on the left. There is a blank column separating them from the column headed G. You never enter anything into that column. It is calculated by the sheet.
- Using the simulation in the right frame, record the values of m1, m2, r, and F in the spreadsheet. NOTE: Enter scientific notation using E notation. For example 1.2 x10^5 woud be entered 1.2E5 and 2.3 x10^-6 would be entered 2.3E-6. That is important for the spreadsheet to perform the calculation properly.
- Perform at 3 runs with different values for m1.
- Perform at least 3 runs with different values for m2.
- Perform at least 3 runs with different values for r.
- Your conclusion will be the value of G, the universal gravitational constant.