3D Moment About an Axis Interactive Assignment

Description

The model built to aid in teaching the concept “3D Moment About an Axis” will serve as an interactive homework assignment meant to teach students how to find the moment about an axis of a physical system. The model can also serve as an in-class supplemental learning tool to show the types of reaction forces and moments that occur on a hinge support. This model will fulfill several functional requirements established by the project sponsor. The model is multi-functional and easy for students to operate. In addition, the model includes a calculation activity for students to perform and helps with visualization of an engineering concept.

Learning Objective

1. Students will develop a better retention of the method of solving for the moment of a force about a given axis

2. Students will develop a physical and more intuitive understanding of how much force is needed to produce a certain moment based on how the physical system behaves due to applied force.

Engineering Topic Covered

The following description of the concept “moment of a force about a given axis” originates in Section 3.11 of the UCSD MAE30A textbook Vector Mechanics for Engineers: Statics :

Procedure for Interactive Homework Assignment

Tools Provided:

• Protractor/Ruler

• Spring scale

• 3 rubber bands of varying thicknesses

1) Measure the dimensions of the model seen in below.

2) Apply a rubber band from the top hook to one of the bottom hooks. An example of one of the possible configurations is seen in the figure below.

3) Measure the angle between the bottom “door” and the ground that results from the application of the rubber band force.

4) While the model is in a state similar to the one shown below, hold the top “door” with your hand. Hook the spring scale to the rubber band on the brass hook attached to the bottom “door”. Pull the spring scale back until the rubber band just barely moves away from the hook as shown in the figure below. Write down the measured force in Newtons that is shown on the spring scale.

5) With the system dimensions, angle, and tension force known, the student has enough information to solve for the moment about the X axis (hinge axis) due the force applied by the rubber band.