Uploaded June 2020 | Updated September 2026, 2 weeks ago
AHGD / BCFE
AHBG / DECF
The "Stack Folding Challenge" is to fold the two lay-outs I show in the video. But the MPMP meta-puzzle is to work out how many different Stack Folding Challenges are possible. That is to say: how many ways can you fold such a piece of paper so that the top-left rectangle is on the top, facing out.
All details about Matt Parker's Maths Puzzles are on the Think Maths website:
think-maths.co.uk/maths-puzzles
think-maths.co.uk/foldingchallenge
If you are already subscribed to the main channel, then, fine, here is my second channel.
youtube.com/mattparker2
You can buy the pieces of paper I was using in the video, signed by me.
ebay.co.uk/usr/standupmaths
All the money from the sale of Stand-up Maths memorabilia goes to charity. WaterAid is working hard to provide sanitation and hand-washing facilities in places which desperately need them, so either bid on the auctions or donate to them directly. wateraid.org/uk/donate/covid-19-emergency-appeal
CORRECTIONS
- Nothing yet. Let me know if you spot anything!
Thanks to Jane Street who are the principal sponsor of my channel. They're amazing.
janestreet.com
Thanks to my Patreon supports who do support these videos and make them possible. Here is a random subset:
Jordan Scales
Ben White
Bob Folk
Claire Greenhalgh
Neil McGovern
Ron Hochsprung
Morgan Butt
James Hall
Nicholas Koceja
Alex Hackman
Support my channel and I can make more videos:
patreon.com/standupmaths
Filming and editing by Matt Parker
Music by Howard Carter
Design by Simon Wright and Adam Robinson
MATT PARKER: Stand-up Mathematician
Website: standupmaths.com
US book: penguinrandomhouse.com/books/610964/humble-pi-by-matt-parker
UK book: mathsgear.co.uk/products/5b9fa76f230ffa140094dc43
Nerdy maths toys: mathsgear.co.uk
AHGD / BCFE
AHBG / DECF
The "Stack Folding Challenge" is to fold the two lay-outs I show in the video. But the MPMP meta-puzzle is to work out how many different Stack Folding Challenges are possible. That is to say: how many ways can you fold such a piece of paper so that the top-left rectangle is on the top, facing out.
All details about Matt Parker's Maths Puzzles are on the Think Maths website:
think-maths.co.uk/maths-puzzles
think-maths.co.uk/foldingchallenge
If you are already subscribed to the main channel, then, fine, here is my second channel.
youtube.com/mattparker2
You can buy the pieces of paper I was using in the video, signed by me.
ebay.co.uk/usr/standupmaths
All the money from the sale of Stand-up Maths memorabilia goes to charity. WaterAid is working hard to provide sanitation and hand-washing facilities in places which desperately need them, so either bid on the auctions or donate to them directly. wateraid.org/uk/donate/covid-19-emergency-appeal
CORRECTIONS
- Nothing yet. Let me know if you spot anything!
Thanks to Jane Street who are the principal sponsor of my channel. They're amazing.
janestreet.com
Thanks to my Patreon supports who do support these videos and make them possible. Here is a random subset:
Jordan Scales
Ben White
Bob Folk
Claire Greenhalgh
Neil McGovern
Ron Hochsprung
Morgan Butt
James Hall
Nicholas Koceja
Alex Hackman
Support my channel and I can make more videos:
patreon.com/standupmaths
Filming and editing by Matt Parker
Music by Howard Carter
Design by Simon Wright and Adam Robinson
MATT PARKER: Stand-up Mathematician
Website: standupmaths.com
US book: penguinrandomhouse.com/books/610964/humble-pi-by-matt-parker
UK book: mathsgear.co.uk/products/5b9fa76f230ffa140094dc43
Nerdy maths toys: mathsgear.co.uk
![How fast is a bullet? [featuring: pendulum calculation]](https://i.ytimg.com/vi/IoYm8lcJQ0o/mqdefault.jpg "How fast is a bullet? [featuring: pendulum calculation]
Thanks to the Cambridge Engineering Department for building the pendulum.
http://www.eng.cam.ac.uk/
Much appreciation to Maria Kettle and Cambridge Engineering Outreach for organising the day.
http://www.eng.cam.ac.uk/events-and-outreach/schools-and-community-outreach
And Hugh was there.
http://www2.eng.cam.ac.uk/~hemh1/
The Cambridge University Rifle Association were super helpful and let us take over their range for most of the day! Katherine Fleck was our expert shooter with infinite patience.
http://cura.soc.srcf.net/
If you have other suggestions for calculating the speed of a bullet: let me know!
CORRECTIONS
- At 3:17 the close-up shows the sliding box already taped to a piece of paper. I only noticed when uploading that we had used this shot from later in the day by accident. It should have been the shot of the box sliding off the pendulum platform. Our solution to fix this problem was to tape it to a piece of paper.
- A few people have asked why we didn’t use a “chronograph”. We did actually use one which detects the movement of the bullet using infrared sensors. But the .22 bullet was too small to trip them.
- People have commented that we didn’t need to use the equation for the period as we know the length of the pendulum and the value of g. But the period is really easy to measure accurately by letting the pendulum swing for ages. Length could be measured fairly accurately (guessing the centre of mass) but g would require an extra assumption.
- Let me know if you spot anything else!
Thanks to my Patreon supports who do support these videos and make them possible. Here is a random subset:
Nicholas Main
Julian Metzler
Amanda Pagul
Christopher Wilson
Claire Greenhalgh
Support my channel and I can make more maths videos:
https://www.patreon.com/standupmaths
Music by Howard Carter
Filming and editing by Trunkman Productions
Sound production by Peter Doggart
Design by Simon Wright
MATT PARKER: Stand-up Mathematician
Website: http://standupmaths.com/
NEW BOOKk: http://wwwh.umble-pi.com
Nerdy maths toys: http://mathsgear.co.uk/")
