Experimenting with Gravity

Junior (Age 8 – 9)

Curriculum Goal

Junior: Matter and Energy

  • Demonstrate an understanding of forces and how they lead to movement and changes in movement.
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Context

  • Students work in groups of two or three.

Materials

  • A variety of four objects of similar shape, but different in mass. For example, tennis balls, golf balls, ping-pong balls, Styrofoam balls. 
    • Students should be able to feel different weights when holding them. 
  • Two sheets of paper per group 
  • A phone or camera able to record slow-motion videos. 

Lesson

  • Separate the students into groups of two or three. Each group will perform experiments to try to understand how gravity affects the movement of different objects as they fall. 
  • Before starting the experiment, each group should have a discussion to hypothesize or predict what they think will happen.  
    • Encourage thinking around as many factors as possible that affect the time it takes for the object to hit the floor (E.g.: mass, shape, orientation, “fluffiness”, flexibility, surface area, etc.) 
    • Make sure they also provide an explanation or reasoning for their predictions. 
  • Each group is given four objects of different mass, two sheets of paper, and access to a device that can record their experiment in slow motion. Students should crumple one of their sheets of paper and leave the other one flat. 
  • Using the items that have been gathered, the students should decide which two they will drop simultaneously. They should be dropped from the same height and the time it takes from when it is dropped to when they hit the floor must be recorded. 
  • Encourage students to think about the mass and shape of the objects and how those factors may influence the speed at which they drop.
  • Ask students to consider how changing the orientation of the objects may influence the outcome when they are dropped. Ask them to perform the experiment again, incorporating some of the changes they’ve brainstormed.  
  • Ask students to record their results by recording slow-motion video and by taking notes. 
  • After the experiment is over, each group will discuss their observations and whether they agree with what they predicted or whether it contradicts it. They can share their findings and theories with the rest of the class.  

Look Fors

  • Are students making informed predictions based on prior experience or knowledge? 
  • Are students able to record their findings in an organized way? 
  • Do students recognize when their observations contradict their intuitions? Do they come up with reasonable explanations for what might be the cause of this? 

Additional Resources

  • This Physics Classroom lesson provides good explanations and visualizations to understand free fall and gravity. 
  • This WIRED article is a good resource to learn more on gravity. There are entertaining examples and further explanation regarding how things fall under the influence of gravity. 
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