JouriAlSharhanJanuary19, 2018 Phase1 ExerciseBicycle Wheel Wheelsare used to provide a more reliable way of transportation rather than having todrag things through rough surfaces.
They reduce friction and provide leverage.(“How Do Wheels Work? | Science ofWheels and Axles.” ) Bicyclewheels are typically over 20 inches in diameter, which is taller than most carwheels. The wheels support therider’s entire weight, mainly due to the way they are formed. The wheels ofbikes are made of a strong hub, a thin rim, and approximately 24 spokes in hightension.
Spokes are the connecting rods found between the bicyclehub and the rim. (“Bicycle Spokes.”).
The use of spokesrather than metal such as cars allows bicycle wheel to be both strong andlightweight and to reduce drag.The way spokes are connected between the hub andrim is important. A bike wheel is generally in tension because the spokes arepulled tight. Since the spokes criss-cross from the rim to the opposite side ofthe hub, the wheel is not as fragile as it appears. When you sit on a bike,your weight pushes down on the hubs, which stretch some of the spokesunevenly.
The spokes are what preventsbuckling from occuring in the wheel when you sit on the bike. The spokes bear the weightunevenly: the few spokes that are near the vertical bear much more load thanthe others. As the wheel rotates, other spokes move closer to the vertical andbegin to take more share of the strain. The constant cycle of sharing morestrain and then relaxing as the wheel rotates eventually leads to having one ofthe spokes failing. After that, a dominoeffect occurs in which the other spokes will have to carry more loads tocompensate for the failed spoke making them more likely to fail too which as aresult makes the wheel buckle. (“BicycleScience – How Bikes Work and the Physics behind Them.”) Geodesic DomeGeodesicdomes are structures that look like half spheres that are made up of manytriangular supports. They come from geodesic designs, which are based on apolyhedron.
A polyhedron is a three-dimensional solid that is made up of manyflat faces. Both pyramids and prisms are examples of polyhedrons. One of themost common polyhedrons used for geodesic dome designs is called anicosahedron, which is a solid shape composed of 20 flat faces. Each face is anidentical equilateral (all sides are equal) triangle. Rotate the edges of thosetriangles slowly toward an imaginary center and eventually you wind up with arough version of a sphere, called a geodesic sphere.
Cut that sphere in halfand you have an approximation of a geodesic dome. They are eye-catching becausethese shapes are so rare in architecture, it’s hard not to let your eyes bedrawn to these domes (Chandler). Thepairing of domes with triangles, makes one extremely durable structure.Triangles are the strongest shape because they have fixed angles. In otherwords, pressure applied to one edge of a triangle, will evenly distribute theforce on the other two sides, which then transmits pressure to adjacenttriangles. That cascading distribution of pressure is how geodesic domesefficiently distribute stress along the entire structure (Chandler). Themanner in which a braced dome behaves depends on the configuration of themembers.
Fully triangulated domes, such as geodesic domes, have a highstiffness in all directions and are kinematically stable. If it is not fully triangulated, it is notkinematically stable when idealised as a truss and stiffnesses varies in differentdirections.Kardysz et al., 2002.The forces in a geodesic network are anequilibrated combination of tension and compression. Tension forces are globaland continuous, while compression forces are local and discontinuous.Buckminster Fuller coined the term tensegrity, a portmanteau of tensionalintegrity, to convey the concept of coherence and resilient elasticity ofgeodesic networks. Ladder A ladderis a structure that consists of two uprights lengths of wood or metal with aseries of bars between them.
Its purpose is to reach higher elevations safely.Over its lifetime the ladder is expected to carry its own weight, the personclimbing it, and the object that the person might carry with them. There are many forces thatact on a leaning ladder when it is in use. First, there are two upward verticalforces. There is an upward vertical contact force from the floor which supportsthe ladder and a vertical upward friction force from the wall where the ladderleans against it.
Combined , these two forces are able to support the weight ofladder. The weight of the ladder acts through the center of gravity in themiddle of the ladder, so it exerts zero torque. However, all the remainingforces do not act through the ladder’s center of gravity and therefore exerttorque. The summation of all torques results in zero. Second, there is ahorizontal force from the wall onto the ladder where they meet. Anotherhorizontal force is caused by the friction between the ladder and the floor.The sum of these forces results in zero making the ladder stable.
Fern A fern is a nonflowering vascular plant thatpossesses true roots, stems, and complex leaves and that reproduce by spores.They belong to the lower vascular plant division, Pteridophyta, having leavesusually with branching vein systems (Walker). In its lifetime, ferns canencounter many loads that they are supposed to carry due to the environmentthey live in. A betterunderstanding of the fern anatomy helps clarify how ferns carry loads. Justlike other plants, ferns have roots, stems, and leaves.
These parts, however,have names that are specific to ferns.TheRhizome or Rootstock is the part of the plant that is responsible for producingroots. They can be thin or thick. They act as the foundation of the fern andoften indicate the growth form of the fern. Rootstock is much like thefoundations used in buildings.
The stemis what connects the root of the plant to the leaves. Its main function isto support the fern and keep itstanding. The leafor frond is what carries the leaflets – the smaller leaves that branch out. Theleaflets are the parts of the frond that are divided. Due to the nature of theleaves branching out forces that act on them branch out as well (Bowe).
Work Cited “Bicycle Science – How Bikes Work and thePhysics behind Them.” Explain That Stuff,13 June 2017, www.explainthatstuff.com/bicycles.html. “Bicycle Spokes.” Materials Engineering – Purdue University,engineering.purdue.
edu/MSE/aboutus/gotmaterials/Sports/lindamood.html. Bowe, Audrey. “All About Ferns: AResource Guide”http://blogs.cornell.edu/naturalistoutreach/files/2013/09/Fern-Guide-27sra8m.
pdf Chandler, Nathan. “How Geodesic Domes Work.” HowStuffWorks Science, HowStuffWorks, 13Sept. 2011, science.howstuffworks.
com/engineering/structural/geodesic-dome.htm. “How Do Wheels Work? | Science of Wheels andAxles.” Explain That Stuff, 24 Oct.
2017, www.explainthatstuff.com/howwheelswork.html. “Ladder.” Dictionary.com,Dictionary.
com, www.dictionary.com/browse/ladder?s=t. Walker, Warren F., et al. “Fern.
” Encyclopædia Britannica, EncyclopædiaBritannica, Inc., 18 Oct. 2016, www.britannica.com/plant/fern.