Engineering Project: Marshmallow Catapult

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SWBAT work through the steps of the engineering design process to plan, build, and test a catapult made to shoot a marshmallow.

Big Idea

Students will act just as real scientists by working through the engineering design process to plan, build, and a test a catapult they made from craft sticks and rubber bands.

Rationale and Preparation

The Why Behind Teaching This: 

The engineering design process is a process used by scientists in the real world.  This process encourages scientific thinking and promotes team work.  This lesson is directly linked to standard 3-5-ETS1-1: Define a simple design problem reflecting a need or want that includes specific criteria for success and constraints on materials, time, or cost.   I provide information regarding the project objective which includes limitations that the group must consider while designing and building.  While researching and planning, students will see a variety of designs and group members may have different ideas that need to be considered.  By working through this process, the activity also covers standard 3-5-ETS1-2: Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem.

Reading standards are connected to this lesson as well through the research process. Standard RI.5.7: Draw on information from multiple print or digital sources, demonstrating the ability to locate an answer to a question quickly or to solve a problem efficiently, is covered through this activity.  Students will be finding models created by other people and considering those models when designing theirs.  They will use the internet for this research and will view a variety of sources during the process.  Math is also connected through measurements made requiring them to apply math practice MP.5: use appropriate tools strategically and MP.6: being precise.  

Additional Lesson Information: 

This lesson takes approximately 2 hours to complete. I do my engineering projects on our school's half day professional development days because I have 2 hours of instructional time with the students.  If you choose to do this activity on a normal school day, it will probably take two days.  Day one would be the planning and design day.  Day two would be the building and testing day.  

Lesson Goal: 

The goal of today's lesson is to promote scientific thinking through the use of the engineering design process.

Success Criteria:

Students will demonstrate their understanding of the process by completing each step of the process: research, plan, build, and test, to create a catapult that can launch a mini marshmallow the greatest distance.    

Preparing for Lesson:

Warm Up:

Guided Practice: 


  • plastic spoons
  • a lot of craft sticks 
  • rubber bands for each group 
  • bag of minimarshmallows  
  • Laptops or computers available for each group to use for research 

Wrap Up: 


Warm Up

5 minutes

I begin today's lesson by telling the students that I am going to show them a video of a competition that our school participated in a couple of years ago. (This video is not of our students but the competition is the same.)

After watching the video I ask students to explain how the catapult worked.  They are able to tell me that you have to pull the arm back to store energy and when it is released it shoots forward causing the ball to fly forward.  I show this video prior to providing them information so that I can assess if they know what a catapult is, and how it works.  If students are not able to tell me how it works, I can provide them with more background knowledge.  My students are able to explain how they work, so I leave the rest of the design up to them to research during the planning part of the process.  If you would like to provide your students with additional background information on the history of catapults, types of catapults, or how they work, you can go to for additional kid friendly information.  

I explain to the students that today, they will be using the engineering design process to build a mini catapult that will shoot a marshmallow.  

Guided Practice

10 minutes

Selecting Groups: 

I usually select groups for them, or use a method so that I know the groups will be diverse in ability levels.  However, I do feel that it is important to allow them to select their own groups sometimes.  I think it is important for them to see how important choosing people that are going to help them meet their goal is.  They choose their own groups today, with the limitation that groups cannot be larger then 4 people.  If anyone is left out, or there are groups with more than 4 students, I move students around.   

Engineering Project Task:  

After choosing their groups, I provide each group with a copy of the Engineering Design Project 3 - catapult task sheet.  I review the objective, materials, limitations, and things that are allowed with them.


90 minutes

Working Through the Process to Create Their Structure: 

Research and Planning: 

I provide each group with the Engineering Project Planning Sheet that they will fill out to help guide them through the planning process.  I remind them that I want to see detailed information about they have learned from their research.  For example, if they watch videos or look up pictures of catapults, what did they learn from comparing the different designs that helped them choose their design.  I do not lead them through the design process because I like them to find their designs on their own, not build one that I have found for them.  I want them to think like scientists and compare different designs and what would be effective and not effective.  

Over the next 30 minutes, students research on laptops and complete their design planning sheet together.  I circulate to ask questions about their research so that I know they are thinking more about what they are looking up and not just looking at pictures.  Groups must submit their planning sheet with the drawing of their planned structure to me prior to receiving their materials.

Once I have approved their planning sheet, they get their materials and begin building. 


Students spend the next 60 minutes building, testing, and making adjustments to their catapult.  

The following videos show students working in groups to construct their catapults.  I selected these videos because these two groups were working together to complete the project.  Everyone had sticks and rubber bands in hand working to construct the model they envisioned.  Both groups seemed to have similar plans as everyone working was connecting sticks to add to the final project.  One group had the plan to build their catapult so that the spoon would be standing upright (group 2), while the other group was just going to lay theirs down.  This will be one thing that will make a big difference when shooting them off and I will point this out to them after testing.   

Video 1 of students building 

Video 2 of students building

As students build, I circulate to keep students on track for time, and to question their design choices.  The majority of groups were building similar structures, but I did notice one group turned their spoon over so that the marshmallow would shoot off the back of their spoon.  I questioned them on their design choose and they said they thought the spoon would spring forward better.  This is something I personally did not even consider and did not expect any of the groups to do so I will pay close attention to how this works out during testing.  

As groups build, they are able to test their catapults, but not with a marshmallow.  I do not allow them to use the marshmallow because when completing these in the past, I have had students smashing them, losing them which leads to ants, and even some eating them after they have been on the floor.  They can use any other object they want as long as they retrieve it after shooting and don't shoot it towards other groups working.  As groups begin finishing their projects, they begin testing with items such as erasers from the end of their pencils, little balls of paper, etc.  They make adjustments to their catapult as they test.  

Wrap Up

15 minutes

Testing their designs: 

After 90 minutes of building, I ask students to clean up their areas and return to their seats.  When everyone is back as their seats we begin testing.  I take the class out into the hall so we can sit on both sides of the hall and watch each group shoot off their catapult.  It is also important to have a large open space to launch the marshmallow so that it isn't obstructed by anything. Each group gets to launch it three times and we take the best distance out of the three.   I was very please that all groups completed a project this time and all traveled a measurable distance.   

The following videos were selected because their launches were successful and they measured accurately.  Some of the other groups designs did not work out as they had planned, which led to some difficulties with shooting off the marshmallows. For example, the group that put their spoon on backwards thinking that it had more flexibility that way, had a very difficult time getting the marshmallow to balance on the back of the spoon prior to shooting it off.  Another group did not build a platform for the catapult to rest on and since they could only use one finger to hold it, they had a difficult time keeping it from falling over before they got it to shoot off.  

I also did not remind students not to play with their marshmallow too much or it would become sticky.  This led to another issue.  A couple of groups smashed their marshmallow down making it sticky and it would not shoot off the catapult.  This may be something you want to point out when handing out the marshmallows.  

Video 1 of students testing shows a group that I had to previously correct on measuring accurately and you can hear me remind them of this in the video.  They corrected themselves and finished this measurement correctly.  You can also see a student playing with his marshmallow in the background and it stick to his hands.  This is what should have been pointed out as something not to do before beginning the testing.  

Video 2 of students testing shows students measuring accurately by measuring at an angle to go straight to the marshmallow.  One reason I chose this video was because it demonstrates why you need a large open space.  Even though we were in the hall, and all students were sitting along one side, their marshmallow went at an angle and almost hit a student.  

Video 3 of students testing was chosen because it shows all students in the group actively involved in the measuring.  No one was standing out while one or two students measured.  I like to see everyone involved in all aspects of the process, including measuring.  

After all groups tested their catapults three times, we compared the designs of those that traveled a far distance to those that traveled a short distance.  The ones that traveled a farther distance were all more upright then those that shot a short distance.  I pulled a spoon back on one of the catapults that was laying almost flat and asked students what happened to the marshmallow with this design.  Groups said that the marshmallows went straight up, some even hit the ceiling.  I pointed out that if our goal was to shoot the marshmallow the highest, this design would be good.  I then showed them how pulling the spoon back on one of the catapults that was almost standing upright shot the marshmallow off in almost a straight line which propelled in forward instead of up.  Since our goal was to shoot the farthest, this was a better design.  

I remind students that one of the activities on our end of the unit choice board projects is to improve one of the engineering design projects we do in class so if they want to take the catapult home and try to improve it, to keep these points in mind.  

Connecting This Engineering Design Project to the Real World: 

To connect this activity to the real world, you can provide students with some reading articles about how students and real scientists have built catapults.  Education World has an article for kids about students building a catapult to shoot pumpkins.