Marshmallow Catapults

The first question I always get from 3rd graders in my IDEA Lab class is "Can we eat the marshmallow?"  And I always respond the same way, "If you have one marshmallow and you eat it, how many marshmallows do you have left?"  "Zero!" they yell out.  This is a good lesson, not just in appreciating what you have but also in terms of constraints.  They have several constraints for this challenge: (1) limited materials and time, (2) they must work in groups of two or three, (3) they can only touch the spoon and the marshmallow when launching their catapult.

I start by introducing the process of Design Thinking that originated at IDEO and Stanford's d.school:

Students are familiar with the concept of empathy from our Social and Emotional Learning (SEL) curriculum.  So they understand what it means to stand in someone else's shoes and to look at a problem from someone else's perspective or needs.  This project doesn't require much empathy since they are designing the product for themselves (and to some extent for me and their homeroom teacher).  The define step is also easy here: I give them constraints and define the challenge: to build a catapult that can fling a marshmallow a long distance.  

The ideate step requires students to work in small groups to brainstorm designs.  This requires cooperation and compromise.  Once a design is decided on, the students build a prototype.  Outside the Open Lab, I've marked every two feet with masking tape to act as our ruler.  Students line up to fire their catapults.  They get two tries and then it's back in the Lab to further revise their designs.  Failure during the testing phase is inevitable and I make sure students expect to fail and also know what to do when they do fail: try again, work together, and hopefully improve upon their prototypes.  One of the tenets of Design Thinking is to quickly iterate through possible designs.  My students test and test again.  Some groups fling the marshmallow 15 feet on their first try while other groups' marshmallows go straight up or even backwards.  But it's mostly smiles and laughter and perseverance.  Frustration is okay, too, as long as it moves the design forward and doesn't negatively impact team dynamics.

This year, students set a school record of 36 feet!  I asked them to reflect on their designs and on the process of working as a team:

What is the best part of the design?

• "The spoon is the best part of the design because you tap the end of the spoon and it launches and it goes very very far."
• "The broken popsicle sticks were the best part of the design.  They kept the cup in place."
• "The best part is the tension in the spoon when we pull the spoon back."
• "The rubber band because it brought great friction."
• "Re-designing because it's fun to take things off and put things on."

What is something you changed during the design process?

• ​"We changed the angle of the spoon because we thought it [would] go farther."
  
• "Adding more rubber bands because the spoon slipped off."
  
• "Turning the cup over because it worked better."
  
• "Using the rubber bands because it gave the spoon a lot of force."
  

What did you find challenging about working in a group?  What did you like about it?

• "I liked blending our ideas."
• "That you had two brains [instead of] one.  It did not work good in the beginning but then it got really good."

— Tatian Greenleaf