Newton's 3rd Law: Explosive Reaction Pairs
Initial Publication Date: August 3, 2009
Summary
Students use miniature explosives to analyze actions and reactions. An Alka-seltzer tablet is sealed in a small film canister with water which sets up a pressure explosion pushing the canister one direction and an adjacent film canister in the opposite direction. Students repeat this set up but vary the mass of the second canister by adding sand. The distances that each canister travels is measured, recorded and later analyzed and discussed.
CollapseLearning Goals
Concepts:
Newton's 3rd Law - For every action there is an equal and opposite reaction (of the same magnitude).
Data Collection and Interpretation - The lab will not be very relevant unless students interpret their data in the context of topics discussed in Physics.
Vocabulary: Action, Reaction, Action-Reaction Pairs, Free Body Diagram, Independent Variable, Dependent Variable
Newton's 3rd Law - For every action there is an equal and opposite reaction (of the same magnitude).
Data Collection and Interpretation - The lab will not be very relevant unless students interpret their data in the context of topics discussed in Physics.
Vocabulary: Action, Reaction, Action-Reaction Pairs, Free Body Diagram, Independent Variable, Dependent Variable
Context for Use
This lab can be used to introduce Newton's laws of motion or can be conducted towards the end of the unit to capitalize on what the students have learned through prior instruction. Much of the experimental design can be tailored to your specific class based on their individual needs. I have conducted this lab in an open inquiry format with higher level students as well as have used as a more cookie cutter format with lower level students.
Students seem to get involved because of the explosions which can energize a lesson and lead to later in depth classroom discussions.
Students seem to get involved because of the explosions which can energize a lesson and lead to later in depth classroom discussions.
Description and Teaching Materials
Materials:
Film Canisters with press-on tops (preferably some clear)
Alka-seltzer tablets
Sand
Track of some sort that the canisters can slide on (I have used meter sticks taped to a lab bench to act as a guide and this seems to work very well)
Lesson can be introduced as students identifying action and reaction pairs (which one feels the more force between the interactions, does mass play a role in the interaction, etc.)
Students will then test their predictions and possible misconceptions using this set-up as a model.
An Alka-seltzer tablet is sealed in a small film canister with water which sets of a pressure explosion pushing the canister one direction and an adjacent film canister in the opposite direction. Students repeat this set up but vary the mass of the second canister by adding sand. The distances that each canister travels is measured, recorded and later analyzed and discussed.
Students, in lab groups, answer the discussion questions included on the attachment.
Lesson concludes with classroom discussion comparing data and interpreting the implications of their findings. Compare this data to real world examples (cannon and cannon ball, you and the earth, etc.) Discuss how mass plays a role in action-reaction pairs. This lab can also lead into discussions of momentum. Student Lab Sheet and Discussion Questions (Microsoft Word 38kB Jul19 09)
Film Canisters with press-on tops (preferably some clear)
Alka-seltzer tablets
Sand
Track of some sort that the canisters can slide on (I have used meter sticks taped to a lab bench to act as a guide and this seems to work very well)
Lesson can be introduced as students identifying action and reaction pairs (which one feels the more force between the interactions, does mass play a role in the interaction, etc.)
Students will then test their predictions and possible misconceptions using this set-up as a model.
An Alka-seltzer tablet is sealed in a small film canister with water which sets of a pressure explosion pushing the canister one direction and an adjacent film canister in the opposite direction. Students repeat this set up but vary the mass of the second canister by adding sand. The distances that each canister travels is measured, recorded and later analyzed and discussed.
Students, in lab groups, answer the discussion questions included on the attachment.
Lesson concludes with classroom discussion comparing data and interpreting the implications of their findings. Compare this data to real world examples (cannon and cannon ball, you and the earth, etc.) Discuss how mass plays a role in action-reaction pairs. This lab can also lead into discussions of momentum. Student Lab Sheet and Discussion Questions (Microsoft Word 38kB Jul19 09)
Teaching Notes and Tips
Goggles needed because of explosions.
This can be dangerous with the wrong group which can aim their projectiles at other classmates.
This can be dangerous with the wrong group which can aim their projectiles at other classmates.
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Assessment
Lab questions at the end of the investigation (see attachment).
Group discussions.
Concept quiz at the end of lab.
Group discussions.
Concept quiz at the end of lab.
Standards
GRADE 9-12 II. PHYSICAL SCIENCE D. Motion
- Newton's third law of motion; Equal and Opposite reactions
GRADE 8 I. HISTORY AND NATURE B. Scientific Inquiry
- Conduct, manipulate and evaluate a classroom experiment
- Newton's third law of motion; Equal and Opposite reactions
GRADE 8 I. HISTORY AND NATURE B. Scientific Inquiry
- Conduct, manipulate and evaluate a classroom experiment