Friction with tug-of-war

Playing a few varieties of tug-of-war is a fun way to experience friction. Students explore what more or less friction feels like.

First, I divided the class into as even teams as possible and then they played tug-of-war in the traditional way.

Here's where it gets interesting. For the second round, I gave the losers of round one gloves to put on. This makes a small change to the amount of grip. The other team still uses their bare hands.

The losing team then received gloves for round three, but their gloves had a large squirt of dish-washing liquid. They were instructed to rub their hands together, then we played tug-of-war again, one team with liquid, one without. This results in a large change to the amount of grip.

Many students had heard of friction and had had everyday experiences with it: rubbing your hands together to get warm in winter, and skidding on the floor.

So what is friction?

Friction is a force that acts between two surfaces in contact producing grip.

I found my students can create a drawing which represents the activity and includes force-arrows to show the pulls. Most of them use the arrows to show the direction of the force and many are using arrows to show whether it is a large or small pull. Some draw many/few arrows, some use thick/thin arrows and some use long/short arrows. This will lead us to discuss scientific conventions and how scientists communicate.

I found my students having difficulty representing the frictional forces. They aren't sure of the direction of force, and most weren't willing to even have a go putting it on paper.

I'm thinking in terms of John Hattie's research, that these students are in the novice phase. I need to develop surface and deep understandings. I need to present and provide opportunities for multiple ways of learning. I need visual, verbal and multimedia forms to provide richer representations. I'm thinking about questions I can pose that will promote thinking. I  need to be clearer with my success criteria, first in my own thinking and then sharing it with students.

Next lesson, we'll review the changes they observed with the different surfaces.I have found relevant, real-life examples: photos of aeroplane crashes on difference surfaces, soles of shoes, and videos of  friction welding, of sand sledding, and a Mythbusters video on interleaved phonebooks. I'll ask those questions and have the students think-pair-share. Which is the best sled to go sledding, and which is the worst? If your plane is going down, which surface would you prefer to land on to stay alive? Which shoes would you choose to play indoor soccer and which to go hiking? We'll be investigating pushing a heavy object on a range of surfaces. We'll come back later and add force-arrows to their drawing to show friction.