2D Moment Demonstration Tool

General Description

An acrylic rigid body connected to a pegboard that can be subjected to multiple tension forces with a changeable pivot point The demonstration tool includes an L-shaped body but the design allows for compatibility with any other preferred shape. The tool is intended to be used for 2D moment visualization in order to efficiently demonstrate this unfamiliar concept to new engineering students. Pipe cleaners can be easily attached at any point along the body to aid in visualization of force vectors, position vectors, and moment arms. Additionally, the tool can function as an interactive 2D moment equilibrium problem, where students will be able to calculate how much mass needs to be added to keep the system balanced.

Engineering Topic Covered

A moment is the rotational effect of a force applied at a distance from a support. In two dimensions, the moment of a force can only be about a point. The formula for 2D moments is as follows:

M = F*r

where F is the magnitude of the force and r is the position vector that extends from the point of rotation to the point of application of the force. The moment arm, M, is represented by a line connecting the point of rotation to the line of action of the force.

Learning Objective

1. Students will demonstrate an understanding of force balance in case of equilibrium (Newton’s first law of motion), the principle of action and reaction (Newton’s third law), and the principle of transmissibility of force for rigid bodies.

2. Students will demonstrate the ability to isolate portions of a structure and to draw their appropriate free-body diagrams.

How to Use

1. Slide the acrylic body onto the fixed center rod at the desired pivot point

2. Clip the lanyard(s) onto the zip ties at desired location(s)

3. Clip the lanyard(s) onto the small bags containing the mass

4. Insert rod(s) and rest the lanyard string(s) over them

5. Adjust lanyard(s) as necessary to avoid the mass resting on the table

6. Fill or remove mass from the small bags to demonstrate the concept of moments or rigid body equilibrium

7. Optional: Attach pipe cleaners around the fixed rod and the holes in the rigid body for visualization of position and force vectors