Lycoming wrote:Well I didn't want to say it, but, yea.
If you plan to go to university, not working well enough to figure this out on little sleep will kill you. Besides, now you're asking me to just straight up give you the answer, which is kind of silly since I already have.
im not good at physics, and i have a sh*te teacher, planning on dropping it at the end of this year.. if you could please just put it in simple words i will be --- happy
This isn't really a homework help forum, especially not if you keep begging for the answer after its been given, then responding angrily when we don't give it to you on a silver platter like it's our obligation to help you.
Louis49 - I think your question is - Why use something stiff and lightweight as a material, lets say carbon fibre to build an F1 car? Well ...Stiff lightweight suspension bits of carbon fiber keep the tires in the best possible contact with the road, a stiff carbon fiber chassis makes the suspension behave. You can't write that down on an exam or assignment like this ... because it sounds ... well not Engineerish enough. If your too tired to have thought it through, your too tired to benefit from more study. Go to sleep will give you back a bit of reason and common sense to solve those A Level exams. Go to bed.
If your really interested in this type of thing, get copies of Advanced Mechanics of Materials and Advanced Mechanics of Composite Materials to study, design a carbon fibre chassis and suspension members then run some simulations with MSC Adams Machinery and Patran - for a more elevated insight into your question.
Last edited by Carlos on 14 Nov 2012, 23:51, edited 1 time in total.
Carlos wrote:Louis49 - I think your question is - Why use something stiff and lightweight as a material, lets say carbon fibre to build an F1 car? Well ...Stiff lightweight suspension bits of carbon fiber keep the tires in the best possible contact with the road, a stiff carbon fiber chassis makes the suspension behave. You can't write that down on an exam or assignment like this ... because it sounds ... well not Engineerish enough. If your too tired to have thought it through, your too tired to benefit from more study. Go to sleep will give you back a bit of reason and common sense to solve those A Level exams. Go to bed.
If your really interested in this type of thing, get copies of Advanced Mechanics of Materials and Advanced Mechanics of Composite Materials to study, design a carbon fibre chassis and suspension members then run some simulations with MSC Adams Machinery and Patran - for a more elevated insight into your question.
Lycoming wrote:This isn't really a homework help forum, especially not if you keep begging for the answer after its been given, then responding angrily when we don't give it to you on a silver platter like it's our obligation to help you.
well i sincerely apologise for reacting angrily when some b*llend told me that i will fail all my a-levels..
When is this due to be submitted?
soon enough for me to join a forum and ask for help
The importance of chassis stiffness is simply the ability to maintain a stable platform for the suspension to operate from and relate to the road surface
anyone still looking, do you think that would suffice?
Perfect Louis49 - Thats a very good answer. If you have to flesh it out:
Study the material characteristics of carbon fibre, in detail - then apply that - with as much depth as possible - to your knowledge of an F1 car's chassis and suspension requirements.
Your doing fine Louis49, don't get downhearted. Stop in again.
Last edited by Carlos on 15 Nov 2012, 00:40, edited 1 time in total.
Lycoming wrote:what would happen if every part of the car flexed around like a big blob of jelly every time any little force was applied to it?
Seriously, thats all your question boils down to. Are you british? Isn't it only like 11PM over there?
yeah mate, was up until 2 yesterday doing it, and had football today so im knackered. thank you for that jelly analogy, its actually helped quite a lot. i just dont think my basic knowledge of stiffness is good enough to apply to a subject i barely know aanything about
Some things need to be as stiff as possible - the chassis for example.
Some things would be useless if they were very stiff - springs & tyres for example.
Most things will be somewhere between the two.
Also there is a parallel material property of ductility (or brittleness). Stiff things are sometimes brittle, and a very stiff car my have good handling but isn't much use if it is brittle because it would shatter like glass under any accidental load. (apologies to purists for my rather crude approximations).
So look at any object and think why it isn't stiffer (like glass) or softer (like an elastic band). A laptop screen for example is stiff enough to hold the screen flat, but you'll also see it has just enough flex so it doesn't snap.
From information already provided (the link to wiki's Young's Modulus, for example) we can say that the amount something deflects when a force is exerted (i.e. how much it moves relative to itself) is inversely proportional to the Young's Modulus (E) of the material its made from:
d is proportional to 1/ E
So, if we double E what happens to the deflection?
The force that causes the deflection can be anything: it could be the load applied by the suspension, it could be the load applied by the wings, it could the load applied in a crash. The system doesn't care why the load is applied it's just interested in the magnitude of the load and the ability of the structure (material) to handle the load.
If you make a structure (in this case the car's structure) from a material of high E then, for a given load, it will deflect less than the same structure made from a material of low E. That is to say that building a bridge from reinforced concrete is better than building the same bridge from cheese.
Look at the wiki entry for Young's Modulus. Look at the material properties table. Compare carbon fibre and steel. Which has the higher E? Which has the higher density (kg/m3)(you might need to look elsewhere fo this but it is fairly intuitive)? Why would you choose a material which has a slightly lower E (carbon fibre) when you could use steel? Would the weight of the steel be a disadvantage compared to its slightly higher modulus?
You say that you're "not interested in it". I assume that you mean you're not interested in the F1 part of the question. If you're actually not interested in the general principles involved then why are you taking physics at A-level? There is no need to have an interest in F1 to form an understanding of material properties and then apply that understanding to a specific question. The great thing about science is that the same rules apply everywhere (within reasonable limits). Thus you figure out what Young's Modulus is, then you ask the question "why might this be useful in a car?". The answer you give might be simple e.g. it'll be better in a crash. That's fine and would be ok as part of your answer, especilly if you explain that for two objects of similar E but differing weights, the lighter object will have lower kinetic energy in a crash (that's a partial give-away answer to an earlier question above). That's not F1; that's basic physics. And it shows an ability to apply basic principles to complex situations. That's a good thing, by the way. You don't need to talk about the installation stiffness of F1 car suspension or anything else specific to cars - you just need to demonstrate that you understand Young's Modulus and what effect it has on objects in general. The F1 bit is a red herring designed to make it sound scary/sexy (depending on your viewpoint).
If you want to be a bit more involved, you might look at glass and aluminium. They have similar Young's Modulus but some very different properties. For example, both aluminium and glass can be used as a material to build floors in buildings. Both will be successful in this application. However, build a car from both materials and then crash the cars to see how each behaves very differently in this situation. It's a useful reminder that focussing on one property of a material isn't necessarily a good idea.
To be honest, if you can't put together a distinction-worthy answer in an hour from basic principles and a little general research and lateral thought then you probably should have taken arts A-levels rather than science A-levels.
If you are more fortunate than others, build a larger table not a taller fence.
I couldn't resist posting this image from 747heavy in a thread about bolts. The bolt has to be stiff enough to clamp things together without any movement, but it also need to be stretchy enough to stretch when the thing it is clamping expands with heat.
