Exploding Carts Notes

Notes:

Teaching Ideas and Suggestions:

This Interactive can be used during just about any stage of a learning cycle on momentum conservation. There are two distinct outcomes from the use of this Interactive. First, in an explosion (such as the one portrayed by the Interactive), the total system momentum is the same before the explosion as after the explosion. Before the explosion, the system of two carts has zero momentum. After the explosion, there is still zero momentum in the system. The red cart has equal momentum as the blue cart, but directed in the opposite direction. When the two momenta vectors are combined, the result is zero. The second concept to be emphasized is that the actual post-explosion velocities are dependent upon object mass. Since both objects must have equal momentum values, the cart with the smaller mass must have the larger post-explosion velocity. The accompanying activity sheet may be quite useful in highlighting these two ideas. View Activity Sheet.

The Interactive could be used as an open-ended student exploration, a teacher demonstration, or a guided activity. An open-ended student exploration could center around a question as simple as one or more of the following:
 

• Use the Exploding Carts Interactive to explore the relationship between the pre-explosion momentum of a system of two carts and the post-explosion momentum of the same system of two carts. How are these two quantities related? Collect some data, make a claim as to the relationship, and support the claim with a reference to your evidence (i.e., supporting data) and a discussion of the reasoning as to how the evidence support the claim.
   
• Use the Exploding Carts Interactive to explore the relationship between the velocities of the two exploding carts of varying mass. Collect some data for different sets of cart masses and organize it in a table. Analyze the data in order to develop a formula that expresses the post-explosion velocity of the red cart (v_red) as a function of the blue carts velocity (v_blue) and the two cart masses (m_red and m_blue). Make a claim (the stated formula) and support the claim with a reference to your evidence (i.e., supporting data) and a discussion of the reasoning as to how the evidence support the claim.
   

See the provided activity for an example of a guided exploration. View Activity.


Our Exploding Carts simulation is now available with a Concept Checker. Do the simulation with the accompanying Activity Sheet. Then follow it up with a Concept Checker.

Related Resources:

• Reading:
  Lesson 2 of the Momentum and Collisions Chapter of the Tutorial is a perfect accompaniment to this Interactive. The following pages will be particularly useful in the early stages of the learning cycle on momentum conservation:
  
  Momentum Conservation Principle
  
  Using Equations as a Guide to Thinking
  
  Momentum Conservation in Explosions
  
   

• Minds On Physics Internet Modules:
  The Minds On Physics Internet Modules include a collection of interactive questioning modules that help learners assess their understanding of physics concepts and solidify those understandings by answering questions that require higher-order thinking. Assignments MC5 and MC6 of the Momentum and Collisions module provide great complements to this Interactive. They are best used in the middle to later stages of the learning cycle. Visit the Minds On Physics Internet Modules.
   

• Curriculum/Practice: Several Concept Development worksheets at the Curriculum Corner will be very useful in assisting students in cultivating their understanding, most notably ...
  
  Action-Reaction and Momentum Conservation
  
  Visit the Curriculum Corner.
  
   
• Labwork:
  Simulations should always support (never supplant) hands-on learning. The Laboratory section of The Physics Classroom website includes several hands-on ideas that complement this Interactive. Two notable lab ideas include ...
  
  Before and After Lab
  What's Cooking? Lab
  
  Visit The Laboratory.

• Science Reasoning Activities:
  Science classrooms should be filled with reasoning activities. There is one related activity in the Momentum and Collisions section of the Science Reasoning Center that will challenge students to employ close reading, data analysis, and logical reasoning. The activity is named ...
  
  Collisions
  
  Visit the Science Reasoning Center.

Visit: Exploding Carts Interactive