A peek inside my lessons: How I teach Work done

I’m prepping a training session on effective explanations for Jan inset and I thought I would share the example I’m going to give of what I think is a pretty decent explanation.

A lot of my thinking around explanations has been framed by the brilliant work carried out by Adam Boxer over the years. While this explanation is mine and he has not seen it, I do think our conversations and the talks I have seen him give are the foundations of my own personal approach. His book Teaching Secondary Science: A Complete Guide contains the best attempt to create a common language around explanatory structure I have read and I recommend it wholeheartedly. Again this is also a science example but hopefully other subject specialisms find aspects of it interesting.

I was coming to the end of the Forces topic in year 11 with my two lower attaining sets and we had circled back around to Work. They had technically covered it during lockdown remote learning last year, but I wasn’t their teacher and questions that had come up during regular retrieval practice had told me this was an area they were completely unfamiliar with. So I decided to spend a lesson on what Work is and the associated formula. Before the explanation I checked and activated prior knowledge with a quick miniwhiteboard quiz on forces and units.

The parts below in italics are the words I say, roughly paraphrased, to give you an idea of how I tell the story.

Without talking, please put pens down and look at the screen. I’m going to explain something important to you. There is no need to write anything down, just listen and watch the screen.

So me and you in the future both work for your removal company. Well to be honest with you, I’ve fallen on some hard times and left teaching and you have kindly given me a job as your employee. So you’re the boss and I have to do as you tell me.

In some ways this scenario might not be perfect. It contains a number of seductive details that might be distracting. If memory is the residue of thought then I need to be careful not to distract students with the idea of removal vans and this fictitious scenario, so they can concentrate on the concepts about to be explained. In this case I think the risk is worth it because the novelty of the situation is more likely to enhance their attention than distract from it. The concept is not so exotic or complex that it risks cognitive overload. Also it’s a bit of fun and the humour helps draw the students in.

We are on a job, here we are *draws stick figures* you’re the boss so you get to wear the hat, and here is our van *draws van* and we have two boxes left to carry to the van. Now you have to choose which box you want to carry. Now here are the boxes, *draws boxes* they are both the same distance away, 5m, but they have different weights. Take a look at the boxes and decide which one you want to carry and which one you are going to make me carry.

As you can see I am not a gifted artist! At this point I will get the students to vote. As it’s a 50:50 I just use a ‘thumb-o-meter’ left/right (not up/down) to choose and narrate the consensus.

Of course! You rightly want me to lift the 250N box and you are lifting the 50N box but why?

I ask a few students using cold call

So we are saying carrying 250N 5m takes more effort than the 50N box. Ok good.

So the following day we go to work and we find ourselves in a similar situation. This time however the boxes are the same weight but different distances. *rubs out boxes and draws as below* 

Which one will you make me carry? 

Thumb-o-meter

Why will you make me carry the box furthest away?

Cold call

Good! The box furthest away requires more effort and as your employee I will gladly do the heavy lifting. So we rightly know already that the distance an object has to be moved affects the total effort we need to put in.

Ok final part. The third day we end up in this situation. *rubs out boxes and draw again*

Now we have 2 boxes with different weights at two different distances. You have to decide which one you want me to lift. You have 10 seconds to turn and talk to your partner before deciding.

With this last question I like to use turn and talk because it gives the students a chance to check their own ideas and make sure they have enough confidence to answer. 

Right3,2,1 stop talking and face this way. Which box should I lift? 

Thumb-o-meter and then follow up questions.

We now agree that it doesn’t matter which box I lift. As the box with a larger weight has a shorter distance the total effort required is the same. 

To calculate how much effort is required we need to take the force and multiply it by the distance travelled *writes force x distance* What are the units? *writes in units after cold call*

Now the word that physicists use for the effort we have to put in is called Work. You use this word a lot in everyday life but, in science, we say the work done on an object is equal to the force applied multiplied by the distance travelled *uses pen to direct attention to formula*

Work done is a kind of energy transfer so what will the unit be?

*writes in joules after cold call*

Great stuff, now please write the formula in your books.

I then move on to guided practice questions using faded examples. A bit like here.

I leave the definition to the end as it allows students to forge a meaning and then integrate the word into that meaning so it builds on prior knowledge and creates a more cohesive schema. Boxer calls this explain then define in his directions of travel. I like to think of this as the teacher’s equivalent of a magician’s prestige. It creates that final ‘ah-ha’ moment and brings it all together nicely.

I hope you found this useful to gain a look inside my lesson. It’s not the only way to explain Work, but it was effective and enjoyable so I’ll probably keep using it. If you have any thoughts or feedback I would welcome them.

*** I recognise that the physics in this example is not technically correct. I realise I risk embedding misconceptions about the direction of force and movement. I could improve this by adding wheels or using a different context involving shelves. I just think the simplicity of this example is powerful that it is worth it for these low attaining students. That’s also why I used the word ‘effort’ even though you can exert effort without doing work. I think it makes it more accessible and gets these students further along the road than they would be with a more correct but confusing story.***

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