General Introduction to the Activities

Overview

Well-designed physical models can substantially enhance the experiential component of engineering education. At a time when many children played more with computer games than physical objects, there is a particular need for mechanics instructors to impart a “gut feel” about mechanical forces and the physicality of structural elements. They also need to instill a connection with the real world, where consequences are real and often irreversible, unlike the virtual worlds of computer games, where humanoids jump 3 stories and are restored from mortal wounds by a keystroke.

The models presented here allow students to feel forces and develop a “gut feel” for mechanics. They also serve as a kind of “analogue computer,” providing instantaneous feedback about the suitability and stability of proposed designs. In addition, they provide a setting within which students can play, explore geometric and mechanical relationships, envision and test designs of their own making, and correct and strengthen their intuition about mechanics.

Most of the models are designed to challenge common misconceptions (see underlined text in the Table below), such as “a semi-circle makes a good arch design” or “a square shape makes a good culvert design”. Many raise implicit questions about construction, such as, “How do you build a long bridge when you can only support it at its ends?” or “In what order should the components of a Gothic cathedral be assembled?” When students have asked questions and had their intuitions challenged, they tend to become interested in the theory needed to explain the enigmatic things they have observed.

The Activities were designed so that students would enjoy them, and so that they were generally straightforward, but with occasional intellectual challenges to maintain the interest of more advanced students. They were also designed bearing in mind that, “If the students are swearing at the equipment or instructions, they are no longer learning.” We also wanted to inspire the students with structures made of beautiful materials and having graceful form.

 

Course Outline

Many of the models and their associated Activities were designed in support of a half-weight course (1.5 lecture hours and 1 tutorial hour per week for 13 weeks) taught in the first term of a 5-year engineering program consisting of 8 academic terms and 6 co-op employment terms. The course was intentionally wrapped around the following elements:

Timing	Activity	Rationale and Intuition Challenge
Lecture 1	Block Stacking	Placing this activity in the first lecture conveys the message that this is not a typical lecture-based course Get students to feel forces and think about them from the very beginning of the course Let them see that mechanics can be fun
Tutorial 1	Beam Reactions	Get students to think about force (reaction) measurement Measure dead and live loads See how reactions change with load type and position See that moment location does not affect reactions, contrary to what most initially thought
Weeks 5 & 8	One of the following:
	Point Equilibrium	Measure force magnitudes (spring scales) and directions (protractors and grid paper) Investigate x- and y-components of forces Compare measured and calculated force components Carry out graphical vector addition See that the vector sum of forces at a point add to zero
	3-Force Body	Investigate equilibrium of 1-, 2- and 3-Force bodies Observe the Principle of Concurrent Forces – try to find a counter-example
	Arches	In general circular arches are not stable Circular arches can be stabilized by making their base wider Shallow arches can be more stable than taller ones There is a direct correspondence between the shape of stable arches and hanging chains
	Suspension Bridge	Understand how deck members, suspenders, main cables and towers work together to carry load Observe the flexibility of a typical suspension bridge deck
	Culverts and Dams	Flat dams and rectangular culverts do not work well Structures with curved surfaces often work better
	Silos and Retaining Walls	The pressure in a silo varies with vertical position The lip of a retaining wall is more effective when under the soil
	Gothic Cathedral	See the role of various flying buttress designs Start to understand and work with spatial and other design constraints Observe that construction sequencing can be crucial

The week-5 Activity was reported in the form of a five-page written report while the Week-8 Activity was reported in the form of a three-minute YouTube-style video.