Here is an activity I’ve used for the past couple of years to help students investigate the variables that affect the force of gravity on objects.
This PHET simulation and assignment really help students understand how manipulating the mass of objects and the distance between them determines how strong the gravitational pull is. It also helps students understand the difference between an independent and dependent variable. Below you will find the PHET Gravity Investigation Resources and some other gravity resources I’ve used over the last few years.
PHET Gravity Investigation Resources:
Additional Gravity Teaching and Learning Resources: