explore-engineering-blog

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Source: https://www.reddit.com/r/educationalgifs/comments/9zel55/gif_i_made_comparing_an_object_sliding_down_a/?utm_source=reddit-android (via reddit user u/ukukuku)

“Gif I made comparing an object sliding down a frictionless incline to various round objects rolling down the incline.” - (u/ukukuku)

The cube sliding down the friction-less incline reaches the bottom first due to the fact there are no restive forces (negligible air resistance) acting on it so it has the greatest acceleration (component of acceleration due to gravity parallel to slope). On the rough slope however although all the objects have the same  mass (linear inertia) they have different moments of inertia (angular mass) which determines the moment needed to produce an angular acceleration, similar to how mass determines the force needed for a certain acceleration. In this case the different shapes of the objects mean that their mass distribution is different and since the moment of intertia for a point mass is the product of mass times the distance from a rotational axis the squared (I = m(r^2)), the moment of inertia for an object with symmetry (like the objects on the slope) will be some fraction of that which it would have if all the mass existed at the distance from the rotational axis (r). This fraction of moment of inertia can be found using calculus. Furthermore the greater rotational inertia the object has the smaller the angular acceleration for a given torque so the objects will roll down the slope with different accelerations reaching the bottom at different points. The cylindrical shell has the greatest moment of inertia as all its mass exists at its radius (the distance from the rotational axis) so reaches the bottom last, and the solid sphere has the least due to its mass being distributed not only perpendicular and at distance r to the rotational axis so it reaches the bottom first. The solid cylinder is 2nd due to the fact although its mass is distributed perpendicular to the rotational axis the majority of its mass is not at distance r, and the spherical shell is last because a majority of its mass exists at distance r from the rotational axis but not all perpendicularly.

Interactive version to play with: https://ophysics.com/r3.html (again credit goes to reddit user u/ukukuku)

Other Souces: http://hyperphysics.phy-astr.gsu.edu/hbase/mi.html (also contains more interactive resources and a really helpful explanation of the calculus and integration involved in calculating the fractions of a moment of inertial) [date accessed: 28/11/18]

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Source: https://www.youtube.com/user/johnnyq90/videos

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Great book Dr. Bernd Thaller

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The trombone is a brass instrument which makes use of a valve slide in order to vary pitch within a tube resonator. Like most brass instruments, it belongs to the lip reed family which means the oscillator which causes the vibrations of air that produce the trombone’s sound is the buzzing lips of the musician themselves, so by varying the tightness (tension) and oscillation speed (frequency) of a musician’s lips the frequency (and therefore pitch) of the stationary wave produced can be changed. However, there is a limit to the capabilities of a human’s lips, and so the valve slide exists to vary the length of tubing which the wave is produced in therefore varying the pitch without the musician changing the way their lips are buzzing. When unravelled and extended fully, a typical trombone contains about 9ft of total tubing making it a fairly heavy instrument, because of this a counterbalance was added which makes utilises the simple ideas of moments so that when placed on a musicians shoulder (the pivot) it is easier to hold. At one end of all that tubing there is a flared end called the bell, it’s main function is to amplify sound produced in the tubing. At the other end of the tubing exists the mouthpiece with a flared conical shape to allow the greatest area to cover the musicians lips and create a closed end where a pressure anti-node exists (verses the pressure node at the open end). The difference in pressure at the open end means that the pressure wave created at the mouth piece is reflected, then this wave will be echoed back by the valve creating a standing wave within the tube, depending on the frequency of the standing wave produced will have a different pitch. 

Sources:

Mostly all the stuff I learnt in A-level Physics lol just applied plus asking my friends who play brass actually well and professionally.

http://mafija.fmf.uni-lj.si/seminar/files/2013_2014/The_physics_of_the_trumpet_(Bostjan_Berkopec).pdf (accessed 21/11/18)

Next post in this fun lil series: Embouchure - what the hell is it and what are the physics of it? 

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Really interesting video, still holds up!

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Little demo video I found to supplement my post on the cantilever principle.

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So I’ve taken up the trombone as part of a charity fundraiser incentive (I have to be able to grade 1 in a year) and playing it with the knowledge I have of stationary waves has definitely helped me pick it up faster but I might do a post or two about the physics of the trombone, its really fascinating to me as a musician and engineering student how these two things often go hand in hand and how a knowledge of one can benefit the other.

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Cantilever Principle:

I saw a photo on here a while back demonstrating the “Cantilever Principle” which was used to build the Forth Bridge so as always I decided to do a quick investigation into it.

A cantilever, in its most basic form, is a rod that extends into free space and is anchored at one side. Placing a load on the end causes the cantilever to bend, the load is supported by tension and redistributed through the rod by compression into the wall, this removes the need for supporting columns or braces. Cantilevers can be both horizontal and vertical, for example a radio tower uses the same principle as a cantilever bridge, anchored to the ground instead of a pillar or riverbank, it also has applications as a chemical sensor.

Alongside this quick exploration I made a few diagrams to aid my understanding I hope they help you too :D

Sources:

http://www.innovateus.net/science/what-cantilever-beam

https://www.reddit.com/r/engineering

https://www.reddit.com/r/AskEngineers/

https://howbridgeswork.weebly.com/cantilever-bridge.html

http://design-technology.org/cantileverbridges.htm

https://sites.ifi.unicamp.br/oteschke/files/2014/03/Aula7-SNOMcantilevar.pdf

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This is why I love running this blog alongside the GCR because so far in the span of a couple of weeks I learnt about vacuum breaks, posted about them here, experienced the ejector on the footplate, examined the pistons and I got to fit a vacuum pipe!

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Vacuum Breaks

So I got a ride on a little 3F today since they’re prepping for the Gala and moving trains all over, and I got to witness the vacuum for the break being created and disturbed as the train was stopped and started. Its really one thing to write about it but to really see it was amazing. Plus I had to help put some pipes and plates back on the 8F so I was underneath the train for a while so I saw the pipe that runs the length of the train up close.

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Great book by  K. Venkata Reddy

Textbook of Engineering Drawing

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Great book K.L.Narayara

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Part 1: Blackbody Radiation and the Ultraviolet Catastrophe

Part 2: Photons, Electrons, and Wave-Particle Duality

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Covered hoppers off the Shenandoah Sub, led by GP40-2 No. 6486, pauses as Amtrak’s Capitol Limited, Amtrak P030, charges away from the Harpers Ferry station. View is from Maryland Heights. April 17, 1994

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What I’ve been up to...

So I’ve been helping clean up the engine in order for the steam pipe to be fitted, the steam pipe is what carries steam to the cylinders where the piston that actually moves the train is, the engineers consider it boring work but I enjoy it and I am really starting to get to grips with how everything fits together and getting to work inside the smoke box was so exciting! Seeing all the boiler tubes and superheater tubes up close there’s nothing like it! The apprentices are alot of fun too! ;)

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Cute little locomotive magazine I found in a charity shop including a great central engine (haven’t worked on that one though :c) should give me some good reading!