5 Piv txwv ntawm cov teeb meem kub
1. Tin uas hnyav 2 kilograms muaj qhov kub tshwj xeeb ntawm 130 J.kg -1 C -1 . Qhov kub uas tin nqus tau los tsa nws qhov kub ntawm 50 o C mus rau 100 o C yog….
Kev Sib Tham
Nws paub tias:
Qhov hnyav (m) = 2 kg
Qhov kub tshwj xeeb ntawm tin (c) = 130 J.kg -1 C -1
Kev hloov pauv kub (Δ T) = 100 o C – 50 o C = 50 o C
Lus Nug: Kub (Q) uas tin nqus tau
Lus teb:
Cov mis cua sov:
Q = mc Δ T
Kev piav qhia: Q = cua sov, m = pawg, c = cua sov tshwj xeeb, Δ T = kev hloov pauv ntawm qhov kub thiab txias
Kub uas tin nqus tau:
Q = (2 kg)(130 J.kg -1 C -1 )(50 o C)
Q = (100)(130)
Q = 13000 Joules
Q = 1,3 x 10 4 Joule
2. Tooj liab nrog lub cua sov tshwj xeeb ntawm 390 J kg -1 o C -1 ntsib kev hloov pauv kub ntawm 40 o C. Yog tias lub cua sov uas tooj liab nqus thaum lub sijhawm hloov pauv kub yog 200 calories, ces qhov hnyav ntawm tooj liab yog ...
Kev Sib Tham
Nws paub tias:
Cov cua sov tshwj xeeb ntawm tooj liab (c) = 390 J kg -1 o C -1
Kev hloov pauv kub (Δ T) = 40 o C
Kub (Q) = 40 Joules
Lo lus nug: Qhov hnyav (m) ntawm tooj liab
Lus teb:
Q = mc Δ T
40 = (m)( 390 )(40 o C)
40 = (m)(390 )(40)
40 = (m)( 390 )(4)
40 = (m)( 1560 )
m = 40 / 1560
m = 0,026 kg
Qhov hnyav ntawm tooj liab yog 26 grams.
3. Dej uas hnyav 20 grams nrog lub cua sov tshwj xeeb ntawm 1 cal g -1 o C -1 pib muaj qhov kub ntawm 30 o C. Txheeb xyuas qhov kev hloov pauv ntawm qhov kub ntawm dej yog tias qhov kub ntawm cov dej nqus tau yog 300 calories!
Kev Sib Tham
Nws paub tias:
Qhov hnyav (m) = 20 gr
Kub pib (T1 ) = 30 o C
Qhov kub tshwj xeeb ntawm dej (c) = 1 cal gr -1 o C -1
Kub (Q) = 300 calorie
Nug: Kev hloov pauv ntawm qhov kub ntawm dej
Lus teb:
Q = mc Δ T
Q = mc ( T2 – T1 )
300 calories = (20 gr)( 1 calories gr -1 o C -1 )(T2 – 30 o C)
300 = (20)(1)(T 2 – 30)
300 = 20 (T 2 – 30)
300 = 20 T 2 – 600
300 + 600 = 20 T 2
900 = 20 T 2
T 2 = 900 / 20
T2 = 45 oC
Kev hloov pauv kub:
Δ T = 45 o C – 30 o C
ΔT = 15 o C
4. Qhov kub uas xav tau los txo qhov kub ntawm 4 kg ntawm cov kua uas muaj qhov kub tshwj xeeb ntawm 500 J/kg K los ntawm 40 oC dhau los ua 20 oC yog…
A. 20 kJ
B. 30 kJ
C. 40 kJ
D. 50 kJ
E. 60 kJ
Kev Sib Tham:
Nws yog paub :
Qhov hnyav (m) = 4 kg
Cov cua sov tshwj xeeb (c) = 500 J/kg K = 500 J/kg Co
Kev hloov pauv kub (delta T) = 40 oC - 20 oC = 20 Co
Nug :
Kub (Q)
Jawb :
Cov mis kub :
Q = (m)(c)(delta T)
Q = (4)(500)(20) = 40.000 Joules = 40 kJ
kJ = kilo Joule
Cov lus teb yog C.
5. Ib yam khoom khov kho uas hnyav 2 kg raug cua sov los ntawm qhov kub ntawm 30oC dhau los ua 100oC, xav tau 7 × 10 cua sov5 Joule. Lub cua sov tshwj xeeb ntawm yam khoom yog…
A. 400 J/kg K
B. 500 J/kg K
C. 700 J/kg K
D. 1000 J/kg K
E. 5000 J/kg K
Kev Sib Tham:
Nws yog paub :
Qhov hnyav (m) = 2 kg
Kub (Q) = 7 × 105 J = 700.000 J
Kev hloov pauv kub (delta T) = 100 oC - 30 oC = 70 Co
Nug :
Qhov kub tshwj xeeb (c)?
Jawb :
c = Q / m T
c = 700.000 J / (2 kg)(70 Co) = 700.000 J / 140 kg Co
c = 5000 J/kg Co
c = 5000 J/kg K
Cov lus teb yog yog E.
