Refutation Text for the Jelly Chair

I said in Episode 6 I would share what I came up with for the Jelly Chair lesson and refutation texts. I did put some thought in to this but think that there is room for improvement. I ended up writing a few sentences for the kids to do:

  • The ancient Greeks thought that arrows were pushed through the air by the god Apollo. We know this is wrong because…
  • Many people think that objects will slow down and come to rest if no resultant force acts upon them but really…
  • A typical GCSE level understanding of balanced forces allows a person to sit on a chair made of jelly. This is false because…
  • Galileo showed that two balls of different weights accelerate at the same rate when dropped.. Before this people thought heavier objects fell faster but this is wrong because…
  • Some people think the International Space Station has no forces acting upon it because it is in Space, the evidence that they are wrong is…
  • When a helicopter is hovering it is very common for people to think that the weight of the helicopter has an equal and opposite force that is the down-force from the rotors. This is wrong because…

I was particularly happy with the last one (though I have no idea if that is an actual misconception or not), and even happier when one of the students said something like:

The down-force is equal to the weight!

They had truly understood the situation, and was able to explain to their partner that the weight and down-force must be equal in magnitude and in the same direction as weight if the helicopter is hovering (not equal and opposite).

As I roamed the class and spoke to the students I was pretty confident the refutation sentences were having impact. The challenge is to use them again and again and embed them in my practice.

The podcast strikes again. Thank you Ben Rogers!

Send Message
Reset Form

7. Ben, Big Ideas and beginnings

 Ben’s Book

Thomas and Robin talk about the podcast’s roots and where it all started, to help all teachers of physics to feel a sense of professional community. You can help by sharing it with your friends, and if you do that you have a chance to win a podcast T-Shirt! The competition lasts until 30th November 2018 and the winner will be announced in the Episode 8.

We were joined by author and all-round lovely man Ben Rogers, whose books The Big Ideas in Physics and How to Teach Them is taking the physics teaching community by storm.  Ben tells us about cognitive science (links below); why he is not opposed to practical work, and how he came up with all the history and characters in the book.

Thomas enthuses about the versorium needle (everyone should make one). 

Robin was on his soapbox again (it happens, just ignore him) encouraging teachers to avoid the temptation to treat new ideas as how they should be teaching, rather to use the ideas to enhance the good practice you’ve built up.

Versorium (needle)

Ben’s References for Cognitive Science

…and finally

Don’t forget to enter our first competition. Win a beautiful podcast T-shirt (in the colour of your choice) by interacting! To win, tell us why you like listening. There are many ways to do this:

Thomas and Robin will pick a winner and announce it in Episode 8.

It remains an engrossing and uplifting adventure making this podcast for you.  You’ve already taken it in directions we weren’t expecting; it really is your podcast, so please get in touch: teachers of physics are our very favourite breed of hero!

The music we use remains One legged equilibrist polka by Circus Homunculus.

Send Message
Reset Form