Investigating Newton's Third Law through Film Canister Cannons
Summary
In this physics lab (best done outside), students will explore Newton's Third Law - 'For every action there is an equal and opposite reaction'. Students will fill empty 35-mm film canisters with water and part of an Alka-Seltzer tablet, place the cap on, and place the canister either cap side down or the cap against a hard surface like the school building. Students will measure the distance the canister is pushed away from the building or into the air. Students will summarize their understanding of Newton's Third Law and suggest applications of the Third Law in everyday life.
CollapseLearning Goals
This activity is designed for students to learn about controlling variables in an experiment, observing, and recording data. Students will also learn to analyze data after changing variables and analyzing differences. Students will also suggest applications of Newton's Third Law to everyday activities.
Context for Use
This activity is intended to demonstrate the effect of Newton's Third Law as a result of a release of chemical energy. This could be done before discussing Newton's Third Law as a way of comparing this Law to Newton's First and Second Laws. This activity is best done outside due to the liquid that will be expelled by the canisters.
Description and Teaching Materials
Students will discuss the order of operation and the data to be gathered. Students will fill an empty film canister with 0.5 cm of water. Start with placing 1/4 piece of an Alka-Seltzer tablet into the canister, replace the cover, and then quickly place the cover end up against a building or cap-side down on the ground. After the explsion, measure how far the canister was pushed from the building or observe how high up the canister was pushed. After several trials, try 1/2 of a tablet. Record results on the data sheet. Gather students and review results. Discuss results in relation to "For every action there is an equal and opposite reaction." Ask for other applications of Newton's Third Law.
Teaching Notes and Tips
Students should wear safety goggles to prevent getting hit in the eye by a film canister or by a splash of Alka-Seltzer. If they should be splashed, rinse the eye and seek medical attention if pain persists.
Several variables to explore are:
1. Different types of film canisters
2. Different amounts of water
3. Different amounts of Alka-Seltzer
4. Adding mass like a fishing sinker to the canister
Several variables to explore are:
1. Different types of film canisters
2. Different amounts of water
3. Different amounts of Alka-Seltzer
4. Adding mass like a fishing sinker to the canister
Assessment
Students will work in groups and fill out data sheets comparing the amount of Alka-Seltzer and the distance the canister was pushed away from the building or up from the ground. Data can be listed in a data table and then graphed. Each group should also list other applications of Newton's Third Law that they have seen in daily life.
Standards
6.II.D. The student will recognize that unbalanced forces acting on an object change the object's speed and/or direction.
8.I.B. The student will specify variables to be changed, controlled and measured.
8.I.B. The student will specify variables to be changed, controlled and measured.