SOLUTION(a) The weight of the bicyc

SOLUTION
(a) The weight of the bicycle frame made from steel is stated to be 30 pounds. The volume of this frame will be
V frame = (30 X 454 g/lb)/(7.8) = 1746 cm3
For aluminum frame the weight will be
Wal = (1746 cm3) X (2.7 g/cm3) X (1 lb/454) grams = 10.38 lbs
Another and simpler way to arrive at this answer is to take the ratio of densities, since the volume is assumed constant.
The weight of the aluminum alloy frame
Walloy = (density of aluminum alloy/density of steel)
X (wt. of the steel frame)
= (2.7/7.8) X 30 lb = 10.38 lb
Thus, the aluminum frame weighs roughly one-third of the steel frame. Similarly, the weight of titanium frame will be
WTi = (density of titanium alloy/density of steel)
X (wt. of the steel frame)
= (4.5/7.8) X 30 lb = 17.3 lb
Finally, the weight of the frame made using carbon-fiber composite will be
Wcf = (density of carbon fiber composite/density of steel)
X (wt. of the steel frame)
= (1.85/7.8) X 30 lb = 7.1 lb
As can be seen, substantial reduction in weight is possible using materials other than steel.
(b) One of the other factors that comes into play is the stiffness of the structure. This is related to the elastic modulus of the material (Chapter 2). For ex- ample, for the same tube dimensions, an aluminum tube will be not as stiff as steel. This will make the aluminum frame bicycle ride “soft.” This effect can be compensated for by making the aluminum tubes larger in diameter and the walls of the tubes thicker. Some other factors to consider are the toughness of each of the materials. For example, even though a carbon- fiber frame is very light, it is relatively brittle. Additional considerations would be the ability to weld or join the frame to other parts of the bicycle, corrosion resistance, and of course, cost.
EXAMPLE 1-2
Ceramic-Carbon-Fiber Brakes for Cars
Car breaks are typically made using cast iron and weigh about 20 pounds. What other materials can be used to make brakes that would last long and weigh less?
SOLUTION
The brakes could be made using other lower density materials, such as alumi- num or titanium. Cost and wear resistance are clearly important. Titanium alloys will be very expensive, and both titanium and aluminum will wear out more easily.
We could make the brakes out of ceramics, such as alumina (Al2O3) or silicon carbide (SiC), since both have densities lower than cast iron. However, ceramics are too brittle, and even though they have very good resistance, they will fracture easily.
We can use a material that is a composite of carbon fibers and ceramics, such as SiC. This composite material will provide the lightweight and wear- resistance necessary, so that the brakes do not have to be replaced often. Some companies are already producing such ceramic-carbon-fiber brakes.

Kết quả (Klingon) 1:

taS() Sep qam Do Duj Dalbogh chenmoH vo' yoDSutlIj naQ ngI' 'e' 30 pounds. ghaH Dalbogh muqLUT VAGH Dalbogh = (30 X 454 g/lb)/(7.8) 1746 cm3 =aluminum ghaH Dalbogh ngI'wal = (1746 cm3) x (2.7 g ghap cm3) x (1 lb ghap 454) grams 10.38 lbs =[latlh 'ej simpler mIw legh jangmeH paw ratio ghu'vetlh, tlhap qaSchoH muq assumed choHbe' mIw vIHechbogh. ghaHDaq BERNARDO.aluminum alloy Dalbogh ngI'walloy (ghu'vetlh aluminum alloy ghap ghu'vetlh yoDSutlIj naQ) =x (wt. Dalbogh yoDSutlIj naQ)(2.7 ghap 7.8) = x 30 lb = 10.38 lbvaj, wa'-wejDIch Dalbogh yoDSutlIj naQ ngI' roughly aluminum Dalbogh. similarly, ghaH titanium Dalbogh ngI'wti (ghu'vetlh titanium alloy ghap ghu'vetlh yoDSutlIj naQ) =x (wt. Dalbogh yoDSutlIj naQ)(4.5 ghap 7.8) = x 30 lb = 17.3 lbtagha', ghaH Dalbogh chenmoH carbon-fiber composite lo' ngI'wcf (ghu'vetlh carbon fiber composite ghap ghu'vetlh yoDSutlIj naQ) =x (wt. Dalbogh yoDSutlIj naQ)(1.85 ghap 7.8) = x 30 lb = 7.1 lbHoch laH legh, substantial reduction qaStaHvIS ngI' DuH Hap 'u' qen, Hatlh yoDSutlIj naQ yoS yIlo'.(b) wa' latlh factors 'e' chenpu' chu' tlham stiffness. related elastic modulus Hap 'u' (Chapter 2). ex-ample, rap tube dimensions, tube aluminum 'oHbe' je stiff je yoDSutlIj naQ. aluminum Dalbogh qam Do Duj lIgh "baQa'." chenmoH laH compensated 'angbogh Da pong aluminum tubes chenmoH weghbogh diameter tubes jeD law' 'IwlIj jeD reD je. 'op latlh factors qel Hoch Hap 'u' toughness. example vabDot pagh quv carbon-fiber Dalbogh SoHvaD chep, relatively brittle. Saturjaj tlhoQ ghaH laH weld pagh Dalbogh muv latlh je, qam Do Duj, corrosion resistance, 'ej luq, cost. EXAMPLE 1-2ceramic-Carbon-Fiber naDchu' puH Dujmotlh chenmoH woDlu'chugh Sut HabmoHwI' lo' 'ej ngI' ghot tu'lu'. mej 20 pounds puH Duj ghor. laH DanoHmeH nuq latlh Hap 'u' naDchu' 'ej QuQ 'eb qaStaHvIS Qav je qup ngI' chenmoH?taSvutmeH naDchu' latlh ghuS ghu'vetlh Hap 'u', such as alumi-num titanium pagh lo'. resistance cost 'ej potlh chu'. titanium alloys SoHvaD wagh 'ej Qop batlhchaj titanium 'ej aluminum latlh Hergh.ceramics. ghaH such as alumina (al2o3) silicon carbide (sic), pagh naDchu' vutmeH maH qaSchoH ghu'vetlh ghuS puS woDlu'chugh Sut HabmoHwI' ghaj batlhchaj. 'ach ceramics tlhoy brittle 'ej vabDot pagh quv majQa' resistance lughaj, fracture chaH Hergh.Hap 'u' ceramics. ghaH such as sic 'ej carbon fibers composite 'e' laH lo' maH. je tuQ-resistance lightweight DuHIvDI' Hap composite 'u' 'ut, vaj 'e' ngaSwI' yuvtlhe' wIngaQmoHta'DI' pIj wej ghaj naDchu'. qabwIj ceramic-carbon-fiber naDchu' chonayta' lIng 'op wey.