Matt & Hugh play with a Brick and derive Centripetal Acceleration

Matt and Hugh play with a tennis ball and a brick. Then they do some working out to derive the formula for the centripetal force (a = v^2/r) by differentiating some vectors.

Dr Hugh Hunt is a Senior Lecturer in Engineering at the University of Cambridge and a Fellow of Trinity College.

This is a new video format idea, so all feedback appreciated!
(Sorry the audio goes a bit out-of-phase; fixing it for this video was beyond my current skill × time, but I'll fix it next time.)

Piano music is an original piece “The River” by Frode-5.

All other music by Howard Carter
Design by Simon Wright

MATT PARKER: Stand-up Mathematician

[outputcoupler]

My physics professor told me that if I ever used the small angle approximation in front of a mathematician, they'd cringe.

Hypothesis confirmed.

[LLHLMHfilms]

Not a great explanation but a Parker square of an explanation.

[sillyfly]

"One vector, two vector
Red vector, blue vector"

[sophieward]

Matt, how does it feel to step into Brady's shoes?

[Borednesss]

You should have tried swinging the brick around instead, just to see what happens. For science =P

[tridecalogism]

Matte and Hue

Their cousins who talk about colour.

[Donkeyiser]

White paper? Does Brady have the brown paper trademarked or something? Surely he would let you use it if you asked..

[JamieThelin]

good thing I can pass this off as M2 revision instead of just me procrastinating

[rrni]

There should be a crossover series with numberphile and sixty symbols where the physicists and the mathematicians talk about how the formulas in physics are derived. In short as a uni student, and as a general science enthusiast I find this video to be superb, and you should, if you can, do more of them.

[LibyaLY]

That small angle approximation is quite the #ParkerSquare

[disnerdforever]

That was a really nice circle he drew freehand 😳

[jonathanCRoberts]

Your pronunciation of centripetal is a classic #parkersquare.

[joao]

"Ok, let's come over here where we have more space... I'm a bit worried of that close to your cabinet"





*Approaches the piano with the brick*

[mwffub]

Rather than "Tennis ball holds brick, " it'd be better to say "Brick holds tennis ball (in orbit)."

[superjez]

I'm lacking my parker square fix.

[lawrencecalablaster]

I really like this new format & show. Please please please make this a thing :)

[RexGalilae]

How I derive *v = rw* (notice that 'w' is omega),
*Length travelled by the ball = the arc length of the circle for the angle theta* (Let's denote it with 0)
*Arc length = r 0* (If we're talking about radians)
*Velocity = Arc length covered / unit time <=> Time derivative of Arc length*
Therefore, *Velocity = r d0/dt = rw*
Done :)


PS. Centri*fugal* force is the better way to look at the ball and brick experiment, imo,  since the ball is pulling the rope outward thereby pulling the brick upwards

[Noremaad]

Aaaand I can officially say that a brick on a string was the most fascinating and educational thing I've seen in some time. Never considered centripetal force as a vertical torque. Not sure what the practical applications would be, but I'm not a physicist engineering solutions to problems with strange properties of matter. Excellent demonstration, though.

[arsenelupin]

The whole time I couldn't help staring at all the fragile and valuable things in the background that could get shattered.

[JanStrojil]

I loved it, I definitely want to see more (and I don't care how much if at all it overlaps with numberphile). Hugh is great, bring him back for more!