Zitsanzo zitatu za mafunso okhudza kukulitsa madera
1. Chitsulo chachitsulo kutentha 20oC ili ndi kutalika kwa masentimita 50 ndi m'lifupi mwake masentimita 30. Ngati coefficient of linear expansion of steel ndi 10-5 oC-1 kenako kuwonjezeka kwa dera ndi dera lonse pa kutentha kwa madigiri 60oC ndi….
Zokambirana
Amadziwika kuti:
Kutentha koyambirira (T)1= = 20oC
Kutentha komaliza (T)2= = 60oC
Kusintha kwa kutentha (Δ)T) = 60oC - 20oC=40oC
Malo oyamba (A)1) = Kutalika x m'lifupi = 50 cm x 30 cm = 1500 cm2
Kuchuluka kwa kukula kwa chitsulo (α)) = 10-5 oC-1
Kuchuluka kwa kukula kwa chitsulo (β)) = 2a = 2 × 10-5 oC-1
Anafunsa kuti: Kuwonjezeka kwa dera (Δ)A)
Kuwonjezeka kwa dera (Δ)A):
ΔA = β A1ΔT
ΔA = (2 × 10-5 oC-1)(1500 cm2)(40)oC)
ΔA = (80) X XUMUM-5)(1500 cm2)
ΔA = 120.000 × 10-5 cm2
ΔA = 1,2 × 105 X XUMUM-5 cm2
ΔA = 1,2 masentimita2
Malo onse (A2):
A2 =A1 +ΔA
A2 = 1500 masentimita2 + 1,2 masentimita2
A2 = 1501,2 masentimita2
2. Mbale ya aluminiyamu yokhala ndi kukula koyenera kwa 24 x 10-6 /oC ili ndi malo a 40 cm2 kutentha kwa madigiri 30oC. Dziwani kutentha komaliza ngati dera la mbale ya aluminiyamu likukwera kufika pa 40,2 cm2.
Zokambirana
Amadziwika kuti:
Kutentha koyambirira (T)1= = 30oC
Kuchuluka kwa kukula kwa aluminiyamu koyenera (α)) = 24 × 10-6 oC-1
Kuchuluka kwa kukula kwa aluminiyamu (β)) = 2α = 2 × 24 × 10-6 oC-1 = 48 x 10-6 oC-1
Malo oyamba (A)1) = 40 cm2
Malo omaliza (A)2) = 40,2 cm2
Kusintha kwa dera (Δ)A) = 40,2 masentimita2 - 40 masentimita2 = 0,2 masentimita2
Anafunsa kuti: Dziwani kutentha komaliza (T)2)
Yankho:
Fomula yosinthira dera (Δ)A) :
ΔA = β A1 ΔT
Kutentha komaliza (T)2):
ΔA = β A1 (T2 - T1)
0,2 masentimita2 = (48 x 10-6 oC-1)(40 cm2)(T2 - 30oC)
0,2 = (1920 x 10-6)(T2 - 30)
0,2 = (1,920 x 10-3)(T2 - 30)
0,2 = (2 x 10-3)(T2 - 30)
0,2 / (2) X XUMUM-3) = T2 - 30
0,1 X XUMUM3 = T2 - 30
1 × 102 = T2 - 30
100 = T2 - 30
100 + 30 = T2
T2 = 130
Kutentha komaliza = 130oC
3. Chinthu chozungulira kutentha kwa madigiri 20oC ili ndi utali wa masentimita 20. Ngati kutentha kuli madigiri 100.oC, utali wozungulira umawonjezeka kufika pa 20,5 cm, ndiye kuti coefficient of linear expansion ya chinthucho ndi….
Zokambirana
Amadziwika kuti:
Kutentha koyambirira (T)1= = 30oC
Kutentha komaliza (T)2= = 100oC
Kusintha kwa kutentha (Δ)T) = 100oC - 30oC=70oC
Utali woyambira (r)1) = 20 cm
Utali womaliza (r)2) = 20,5 cm
Anafunsa kuti: Kuchuluka kwa kukula kwa dera la chinthucho (b)
Yankho:
Gawo loyamba la bwalo (A)1) = π r12 = (3,14)(20 cm)2 = (3,14)(400 cm2) = 1256 cm2
Gawo lomaliza la bwalo (A2) = π r22 = (3,14)(20,5 cm)2 = (3,14)(420,25 cm2) = 1319,585 cm2
Kuwonjezeka kwa dera la bwalo (Δ)A) = 1319,585 masentimita2 - 1256 masentimita2 = 63,585 masentimita2
Fomula yosinthira dera (Δ)A) :
ΔA = β A1 .T
Chiŵerengero cha kukula kwa dera:
ΔA = β A1 .T
63,585 masentimita2 = β (1256 masentimita2)(70) oC)
63,585 = β (87920 oC)
β = 63,585 / 87920 oC
β = 0,00072 /oC
β = 7,2 X XUMUM0-4 /oC
Kuchuluka kwa kukula kolunjika (α)):
β = 2 α
α = β / 2
α = (7,2) X XUMUM0-4/ 2
α = 3,6 X XUMUM0-4 oC-1
