Question

The coefficient of linear expansion of iron is 1.0 x 10-5 per oC. The surface area of an
iron cube, with an edge length of 5.0 cm, will increase by what amount if it is heated
from 10 oC to 60 oC?

Answer 1

i need the answer too...all ears

Answer 2

first get coeffecient of area expansion( beta ) by multiplying coeffiicient of linear expansion(alpha) by 2
then use the formula

\[\huge \delta l/l =\beta t\]

Answer 3

\[\Delta A =A 2 \alpha \Delta T\]

Answer 4

what about this? i don't recognise your formula

Answer 5

srry i made a typind mistake

Answer 6

its dA/A=beta t

Answer 7

can u get to the answer nw?

Answer 8

so its (2)*(1*10^-5)*(5cm)*(50degrees) ?

Answer 9

= 5*10-3 the answer from the solutions is 0.15cm^2

Answer 10

same i cant get 0.15cm^2

Answer 11

i think im going to smash my head into the wall

Answer 12

it;s a cube so it expands not only alone the edge of 5cm..
I think you need to calculate the area of the outside of the cube first..

Answer 13

using La delta T?

Answer 14

so it has 6 sides 5cm by 5cm

Answer 15

yes
exactly.. its (5*5)*6 for the area in cm.. convert that to meters and than just multiply by La*dT

Answer 16

but than you still don't get .15cm2..

Answer 17

lol yea...

Answer 18

question.. the liniar expesion.. what the unit? m per degrees c?

Answer 19

yeh you get 1.5*10^-3cm^2

Answer 20

how?
I get something with 7.5...

Answer 21

per degree

Answer 22

same with aqua got 7.5E-4

Answer 23

because its area i thought you use this ΔA=A2αΔT

Answer 24

yes but what per degree...

Answer 25

units in this questions just say per degreee

Answer 26

dimensionless according to the book...doesn't state anything

Answer 27

do you go to UTS jade?

Answer 28

got it

Answer 29

how?

Answer 30

leave it in cm when doing the calculation

Answer 31

5*5*6*50*2*10^-5

Answer 32

why times 2?

Answer 33

because its area i got it from some other guy on this site...i found a website http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/thexp2.html

Answer 34

area is 5*5*6

Answer 35

that supports this...yeh i go to uts

Answer 36

or 5*2*6...

Answer 37

nah 5*5 is area...*6 for 6 sides

Answer 38

wow! small world jade, i go to uts too

Answer 39

than why did you do the * 2?:P

Answer 40

and theres no 2 in my formula sheet, thats odd

Answer 41

\[\beta\]

Answer 42

hang on

Answer 43

\[\beta = 3 \]

Answer 44

b=3a

Answer 45

\[\beta=3 \alpha\]

Answer 46

\[2\alpha\]

Answer 47

for area

Answer 48

you are making no sense at all :P

Answer 49

yea..

Answer 50

β=3α is for volume
Surface Area =2α

Answer 51

then again.. it's not my question so if you get the answer than that's what's most important XD

Answer 52

volume expansion

Answer 53

understand now?

Answer 54

that's why I was wondering bout the units of the lineair expension.. usually, expansion is raleted to volume not surface area.. but it's possible to relate it to either one.. which is why you need the to know the unit...

Answer 55

so 2a is just a rule?

Answer 56

yeh compare the equation for linear expansion and volume expansion...to do volume expansion you multiply alpha by 3. for area its 2

Answer 57

the area is always width times lenght.. if all sides are equal that is 2 times alpha or whatever you want to call the length of the sides

Answer 58

so why isnt there a 2 in the La delta T formula?

Answer 59

because that's for the expansion of 1 cm/m or whatever your unit is... anyway I'm going home.. see yah later

Answer 60

because its linear

Answer 61

alright thanks

Answer 62

no worries...didn't know uts people came on here. you uts too aqua?

Answer 63

gonna get hammered in the physics finals

Answer 64

lol yeh thats what it feels like

Answer 65

engineering?

Answer 66

yeh

Answer 67

jesus, we might even be in the same class

Answer 68

yeh maybe. but i am not going to disclose my identity here lol

Answer 69

lol yea

Answer 70

you have to get 40% for the final...to pass...if i don't pass im probably going to drop the degree..not worth it

Answer 71

4 days...not much time at all