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.