Author: Michele Deacon, Beth Kennedy, Roberta Gangl, Susan Franz, Chris Bode, Kathie Owens
Source: Frank Potter's Science Gems (internet site)
Through several trials of dropping objects from various levels of a jungle-gym, students will be able to find out more about gravity, forces, and motion.
What should students know as a result of this lesson?
What should the students be able to do as a result of this lesson?
Review the meaning of a hypothesis as an educated guess based on previous experience. To get the students ready to formulate a hypothesis, have them take a few minutes to think about what has happened to objects they have dropped in the past. Be sure to emphasize to students that it is perfectly all right to make an incorrect hypothesis and that scientists do this all the time. Brainstorm a class hypothesis about what controls how objects will move when dropped. Do not have a lengthy discussion about "gravity" at this point. The focus of the lesson at this point is the experimental process.
Before going out to the playground, pose some of the following questions for students to begin thinking about: What makes things fall when you drop them? Do heavy objects seem to fall faster, slower or the same speed as lighter objects? How does the distance dropped affect the fall and the landing? Would an elephant fall differently than a peanut?
Posed problem: Describe the motion of falling objects: how long does it take objects to hit the ground when dropped from the same height? Describe the crater made in soft sand when the object hits the ground: how wide and how deep is the crater?
Assessment: Monitor the class discussion to be sure that students have some knowledge of making hypotheses and understand the posed problem.
Distribute one experiment report to each group of students. Have the student groups select three objects to be dropped. Explain to the students that their three objects should vary in size, shape and mass. Students should then record their selected objects in the appropriate column of their table and make a hypothesis about the nature of the fall and the relative size of the crater they think will be produced. Take students out to the jungle-gym area where the teacher has prepared the landing areas with large piles of soft sand. We suggest that more than one landing area is used so that more than one group may conduct their tests at a time. We also suggest that a drop of at least 2 meters should be used. Releasing from a greater height is more easily measured.
Take turns allowing the investigator in each group the opportunity to drop its objects one at a time. Have the timer take the time of landing and measure the width and depth of the crater formed. Before the next drop happens the landing area will need to be smoothed out. We suggest allowing the students to switch roles, unless a student does not like climbing to the top of the jungle gym.
Assessment: Monitor the students as they perform the tests and collect data. Be sure that they are on task and working safely. Monitor the discussion for signs of data analysis and links to force, motion, and gravity.
Pose a new problem for the students. Ask them to predict the motion and impact on the ground of several objects used in the lesson if the motion is adjusted from a straight vertical drop to a slide down a gutter used like an inclined plane. Return to the playground and conduct a demonstration using this new set up. Back in the classroom discuss the findings within the context of motion, forces and gravity.
Assessment: Show students objects similar to, but not identical to, the objects used in this experiment. Have students predict the fall (time and motion) and the crater formed in the sand pile upon impact. Using their findings from the experiment they should be able to accurately justify their predictions. Ideally their writings should show understanding of gravity, motion, and forces.
Have students think about some objects they might have at school or at home to test how different objects fall when they are dropped. Remind students to pick objects that are different sizes, shapes and masses and that the objects they select will not break.
Exercise caution when climbing to the top of the jungle gym. Do not allow students to stand too close to the falling objects or to the sand pile into which they drop. Pick objects to drop that are sturdy with no possibility of shattering upon impact. The student(s) raking the sand pile(s) should wear goggles.
Gravity affects our everyday lives.
Show students objects similar to, but not identical to, the objects used in this experiment. Have students predict the fall (time and motion) and the crater formed in the sand pile upon impact. Using their findings from the experiment they should be able to accurately justify their predictions. Ideally their writings should show understanding of gravity, motion, and forces.
Grouping Suggestions: Groups of three. Students take turns being investigator, timer, and recorder.
Pacing/Suggested Time: 2 Science periods.