Robo Arm

Design Squad Nation, WGBH Boston
Type Category
Instructional Materials
Student Guide , Lesson/Lesson Plan , Model , Animation/Movie , Instructor Guide/Manual , Rubric , Activity
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be "fully aligned," the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.



This fun activity is one of five in a series of space based engineering challenges developed by NASA and Design Squad where students are engaged in implementing the Engineering Design process to build a robotic arm that can lift a cup off a table using cardboard strips, brass fasteners, paper clips, straw, string, tape and a cup. The activity includes an instructors guide, questioning techniques, discussion questions, extension activity, a rubric, and 3 short video clips that enhance the purpose of the activity and it's relevance to NASA.

Intended Audience

Educational Level
  • Grade 3
  • Grade 5
  • Grade 4
  • Upper Elementary
Access Restrictions

Free access - The right to view and/or download material without financial, registration, or excessive advertising barriers.

Performance Expectations

3-PS2-1 Plan and conduct an investigation to provide evidence of the effects of balanced and unbalanced forces on the motion of an object.

Clarification Statement: Examples could include an unbalanced force on one side of a ball can make it start moving; and, balanced forces pushing on a box from both sides will not produce any motion at all.

Assessment Boundary: Assessment is limited to one variable at a time: number, size, or direction of forces. Assessment does not include quantitative force size, only qualitative and relative. Assessment is limited to gravity being addressed as a force that pulls objects down.

This resource was not designed to build towards this performance expectation, but can be used to build towards it using the suggestions provided below.

Comments about Including the Performance Expectation
The Robo Arm is a lever system. Ask students what part is the fulcrum? Which part is the lever arm? What is the effect of moving a fulcrum, changing the length of a lever arm, or changing the string’s attachment point? The brass fastener is the fulcrum and the cardboard is the lever arm. Changes will alter the force required to move the lever. It will be helpful to make the connection between balance/unbalanced forces and the forces created by the lever system. To fully address the physical science aspect of forces on the motion of an object, further activities should be done. Students can explore activities that compare the effects of a gentle force and a harder force on an object in motion such as a pendulum.

3-5-ETS1-1 Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost.

Clarification Statement: none

Assessment Boundary: none

This resource is explicitly designed to build towards this performance expectation.

Comments about Including the Performance Expectation
It is important to relate this activity to NASA's exploration of the solar system to give students the real life meaning of their challenge before they begin the activity. A short video of how a NASA scientist uses robots in space exploration is linked to the page. Equally important is that the students should have already been introduced to the muscular/skeletal systems and levers prior to engaging in the engineering design process. Introduce the lesson to the students by discussing how robotic and human arms have similarities. Both use flexible parts (string or muscle) to move rigid parts (cardboard or bone). The string’s, or muscle’s pull is directed by a guide (straw or tendons), and the guide’s position affects the arm’s efficiency. Finally, the brass fasteners mirror our joints. Make the “strings” (tendons) in the hand visible by having kids lift their fingers up and back. Students should be familiar with the Engineering Design Process and a visible copy may be made available. The students will brainstorm with partners or groups using only the materials provided (precut cardboard, paper clips, string, straw, brass fastener, paper cup) to design an arm that can pick a paper cup a couple of cm off their desk. Discuss with the students that the challenge may not work the 1st, 2nd, or 3rd time they build their robotic arm. Students may have to change the location of the string on the cardboard numerous times to get the sections of the 'arm' moving in the most 'efficient' way. Encourage students to work together to to find solutions to make the arm work better. To fully address the physical science aspect of forces on the motion of an object, further activities may be done.

Science and Engineering Practices

This resource appears to be designed to build towards this science and engineering practice, though the resource developer has not explicitly stated so.

Comments about Including the Science and Engineering Practice
Students will continually be making observations to test and retest their designs. Students will be following the design process each step of the way from identifying the problem, brainstorming the design, building, testing, evaluating and redesigning again to achieve the best possible movement of the robotic arm as they attempt to pick up objects.

Disciplinary Core Ideas

This resource was not designed to build towards this disciplinary core idea, but can be used to build towards it using the suggestions provided below.

Comments about Including the Disciplinary Core Idea
The success of the arm design will be if the students can lift the cup (or the challenge for a few students to use their robo arms to lift a heavier object collectively). Through problem solving and collaborative group work, students can see how some arms worked to achieve the goal in a better way and build upon those student's designs. Discuss with the students how gravity is pulling down on the cup so the 'arm' needs to be able to exert enough force. To fully address the physical science aspect of forces on the motion of an object, further activities should be done.

Crosscutting Concepts

This resource appears to be designed to build towards this crosscutting concept, though the resource developer has not explicitly stated so.

Comments about Including the Crosscutting Concept
Reiterate to the students that each part of the robo arm (cardboard, fasteners, string and guidelines) all serve to make the arm function. They need to brainstorm and redesign the placement of each part to make the arm work efficiently.

Resource Quality

  • Alignment to the Dimensions of the NGSS: As far as 3-5 ETS1 Engineering Design, this resource is Superior because it includes specified criteria for success (the arm functions well and can pick up an object) while giving the students constraints on materials, time and cost. The students are encouraged to follow the engineering design process and redesign as they see a better solution may be available by moving around the fulcrum or string guides. More lessons on net force are needed to make this a superior resources.

  • Instructional Supports: This lesson includes specific instructions in the instructor and student guides, clear steps to attempt the challenge, extension activities, short video clips to align activity with real world problems, assessment questions and a rubric for assessment.

  • Monitoring Student Progress: Students are encouraged to design and re-design their robotic arm to make it work better. Assessment questions and the rubric help to guide the progress of the lesson. To best monitor student progress, have them record the changes made to their prototypes and observations of how it performed each time they redesigned in their journals. This could yield valuable formative assessment data regarding their understanding and application of the science concepts.

  • Quality of Technological Interactivity: This is a strong rating as the students are designing and interacting with a prototype of technology. Although the 3 video clips are limited due to not being interactive, they are very useful and help to give background information to the students. Each video is approximately 3 minutes in length, and includes a profile of a NASA engineer. These clips are short and bring the point of the performance expectation (using the Engineering Design) to real world problems that NASA faces in designing robots to help with exploration.The clip of a NASA Robotics engineer showing how humanoid robots can do the work of humans on space missions portrays to the students how engineers actually use the engineering design process to solve problems and make work easier for humans.