Tag Archives: dynamics

Formative experiences

A few weeks ago, I wrote about how we all arrive in the classroom with different experiences that are strongly influenced by the conditions in our formative years.  When I talk about this process in workshops on teaching, I invite attendees to tell us about something that has influenced their approach to learning.  However, I kick-off by sharing one of mine: I joined the Royal Navy straight from school and so I arrived at University having painted the white line down the centre of the flight deck of an aircraft carrier but also having flown a jet.  This meant that my experience of dynamics was somewhat different to most of my peers.  It’s amazing the life experiences that are revealed when we go around the room at these workshops.  Feel free to share your experiences and how they influence your learning using the comments section below.

CALE #2 [Creating A Learning Environment: a series of posts based on a workshop given periodically by Pat Campbell and Eann Patterson in the USA supported by NSF and the UK supported by HEA]

Photo by Pedro Aragao [Creative Commons Attribution-Share Alike 3.0 Unported]

Popping balloons

Balloons ready for popping

Balloons ripe for popping!

Each year in my thermodynamics class I have some fun popping balloons and talking about irreversibilities that occur in order to satisfy the second law of thermodynamics.  The popping balloon represents the unconstrained expansion of a gas and is one form of irreversibility.  Other irreversibilities, including friction and heat transfer, are discussed in the video clip on Entropy in our MOOC on Energy: Thermodynamics in Everyday Life which will rerun from October 3rd, 2016.

Last week I was in Florida at the Annual Conference of the Society for Experimental Mechanics (SEM) and Clive Siviour, in his JSA Young Investigator Lecture, used balloon popping to illustrate something completely different.  He was talking about the way high-speed photography allows us to see events that are invisible to the naked eye.  This is similar to the way a microscope reveals the form and structure of objects that are also invisible to the naked eye.  In other words, a high-speed camera allows us to observe events in the temporal domain and a microscope enables us to observe structure in the spatial domain.  Of course you can combine the two technologies together to observe the very small moving very fast, for instance blood flow in capillaries.

Clive’s lecture was on ‘Techniques for High Rate Properties of Polymers’ and of course balloons are polymers and experience high rates of deformation when popped.  He went on to talk about measuring properties of polymers and their application in objects as diverse as cycle helmets and mobile phones.

Connecting robotic touch and vision

katherine kuchenbeckerSome months ago I wrote about soft robots that could delicately pick up fragile objects [see my post entitled ‘Robots with a delicate touch’ on June 3rd, 2015]. These robots, developed by George Whiteside’s research group, went some way towards mimicking the function of our hands.  However, these robots are numb because they have no sense of touch.  Think about how hard it would be to strike a match or pick up an egg without your sense of touch. Katherine Kuchenbecker from the University of Pennsylvania is working on robots with tactile sensors that detect pressure and vibrations.  This sensitivity transforms their ability to perform delicate tasks such as picking up an egg, or perhaps more significantly perform surgery.  I listened to Professor Kuchenberger speak at a meeting at the Royal Society on ‘Robotics and Autonomous Systems’ where she put us off our lunch with some gory videos on robot-assisted surgery. You can watch them at her website. Her vision is of robots that connect vision and touch, which is of course what we do effortlessly most of the time.

Meta-representation competence

toasterdrawingOk, it’s a challenging title and a strange thumb-nail diagram but stick with it!  Last week I was giving revision lectures for my first year class in thermodynamics which is why my post was about problem-solving.  I mentioned the difficulty in persuading students to represent problems pictorially.  It is called meta-representational competence.  It is a knowledge of when visual representations are likely to be appropriate, how to create them and how to interprete them, according to Disessa and Sherin (2000).

It is hard because you need to become comfortable with the slow and uncertain process of creating representations and exploring the space of possibilities, to quote Martin and Schwartz (2014).  This is achieved through practice. Oh, and now we are back to students testing their skills against problems set by their tutors.  It is what engineers learn to do as part of their formation.  They might not realise it but their meta-representation competence is one of the attributes that make them so attractive to employers.

Now, what about that thumb-nail.  Well, it is my picture drawn as part of the staff answer to the Everyday Engineering Example below, which was given to our new engineering students in their first week at university and subsequently discussed with their personal tutor. Can you solve it with my sketch?  Answers via the comments…

Dynamics Example:

A two-slice toaster is switched on by depressing a slider which causes the slices of bread to fall downwards into the toaster between heating elements and also extends a pair of springs at each end of the toaster. When the toast is ready a pair of triggers releases both springs simultaneously, which in turn cause the toast to ‘pop’ up. If the toast is to just not jump completely out of the toaster when it is ready and in the ‘off’ position rests with two-thirds in the toaster, calculate the force that must be applied to the slider when switching on the toaster. Neglect the weight of the mechanism and assume that there are no losses.


Disessa AA & Sherin BL, Meta-representation: an introduction, J. Mathematical Behaviour, 19(4):385-398, 2000

Martin L & Schwartz DL, A pragmatic perspective on visual representation and creative thinking, Visual Studies, 29(1):80-93, 2014.

Martin L & Schwartz DL, Prospective adaptation in the use of external representations, Cognition and Instruction, 27(4):370-400, 2009.