Qhov ceev yog ib lub tswv yim tseem ceeb hauv kev kawm txog physics uas qhia rau ntawm qib junior high school, tshwj xeeb tshaj yog hauv qib 7. Lub tswv yim no pab cov tub ntxhais kawm nkag siab txog qhov hnyav ntawm ib yam khoom cuam tshuam li cas rau nws qhov ntim. Hauv tsab xov xwm no, peb yuav tham txog lub ntsiab lus ntawm qhov ceev, cov mis siv, thiab qee qhov piv txwv teeb meem los ua kom cov tub ntxhais kawm nkag siab meej.
Kev Txhais ntawm Qhov Ceev
Qhov ceev yog qhov ntsuas ntawm qhov sib sau ua ke ntawm ib yam khoom qhov hnyav hauv ib qho ntim. Hauv lwm lo lus, qhov ceev qhia txog qhov ceev ntawm ib yam khoom. Qhov ceev tuaj yeem qhia tau los ntawm kev siv cov mis:
\[ \rho = \frac{m}{V} \]
Qhov twg:
- \(\rho\) (nyeem: rho) yog qhov ceev.
- \(m\) yog qhov hnyav ntawm cov khoom.
- \(V\) yog qhov ntim ntawm cov khoom.
Lub chav SI ntawm qhov ceev yog kilograms ib cubic meter (kg/m³). Txawm li cas los xij, grams ib cubic centimeter (g/cm³) kuj feem ntau siv rau hauv cov ntsiab lus me me.
Qhov Tseem Ceeb ntawm Qhov Ceev
Qhov ceev yog ib qho khoom tseem ceeb heev vim tias:
1. Kev Txheeb Xyuas Cov Khoom Siv: Txhua yam khoom siv muaj qhov ceev tshwj xeeb. Los ntawm kev paub qhov ceev, peb tuaj yeem txheeb xyuas cov khoom siv.
2. Tsim thiab Engineering: Hauv kev tsim khoom, qhov ceev ntawm cov khoom siv yuav tsum tau xav txog los txiav txim siab lub zog thiab kev ruaj khov ntawm cov qauv.
3. Kev Siv Hauv Kev Lag Luam: Kev siv ntom ntom yog siv rau hauv ntau yam kev siv hauv kev lag luam xws li kev tsim khoom siv, hniav nyiaj hniav kub, thiab lwm yam.
Cov Qauv Ceev
Yuav xam qhov ceev, peb siv cov mis uas tau hais los saum toj no:
\[ \rho = \frac{m}{V} \]
Piv txwv ntawm daim ntawv thov Formula
Xav tias peb muaj ib yam khoom uas hnyav 200 grams thiab ntim 50 cm³. Tom qab ntawd, nws qhov ceev tuaj yeem suav tau raws li nram no:
\[ \rho = \frac{200 \, \text{g}}{50 \, \text{cm}^3} = 4 \, \text{g/cm}^3 \]
Cov Lus Nug Piv Txwv thiab Kev Sib Tham Txog Qhov Ceev
Piv txwv lus nug 1
Lo lus nug:
Ib lub pob zeb muaj qhov hnyav li 300 grams thiab qhov ntim li 100 cm³. Xam qhov ceev ntawm lub pob zeb.
Kev Sib Tham:
Nws paub tias:
– Qhov hnyav (m) = 300 grams
– Ntim (V) = 100 cm³
Siv cov qauv ntom ntom:
\[ \rho = \frac{m}{V} = \frac{300 \, \text{g}}{100 \, \text{cm}^3} = 3 \, \text{g/cm}^3 \]
Yog li ntawd, qhov ceev ntawm cov pob zeb yog 3 g / cm³.
Piv txwv lus nug 2
Lo lus nug:
Ib daim ntoo muaj qhov loj li ntawm 2.000 cm³ thiab qhov ceev yog 0,6 g/cm³. Qhov hnyav ntawm daim ntoo yog dab tsi?
Kev Sib Tham:
Nws paub tias:
– Ntim (V) = 2.000 cm³
Qhov Ceev (rho) = 0,6 g/cm³
Siv cov mis hloov pauv kom pom qhov hnyav:
\[ m = \rho \times V = 0,6 \, g/cm^3 \times 2.000 \, cm^3 = 1.200 \, g \]
Yog li, qhov hnyav ntawm lub thaiv ntoo yog 1.200 grams lossis 1,2 kg.
Piv txwv lus nug 3
Lo lus nug:
Ib yam khoom uas hnyav li 500 grams muaj qhov ceev ntawm 2,5 g/cm³. Qhov ntim ntawm yam khoom yog dab tsi?
Kev Sib Tham:
Nws paub tias:
– Qhov hnyav (m) = 500 grams
Qhov Ceev (rho) = 2,5 g/cm³
Siv cov mis hloov pauv kom pom qhov ntim:
\[ V = \frac{m}{\rho} = \frac{500 \, \text{g}}{2,5 \, \text{g/cm}^3} = 200 \, \text{cm}^3 \]
Yog li, qhov ntim ntawm cov khoom yog 200 cm³.
Piv txwv lus nug 4
Lo lus nug:
Yog tias ib lub hlau uas muaj qhov ntim ntawm 250 cm³ muaj qhov hnyav ntawm 2 kg, xam qhov ceev ntawm cov hlau hauv cov units ntawm kg/m³.
Kev Sib Tham:
Nws paub tias:
– Ntim (\(V\)) = 250 cm³ = 0,00025 m³ (vim 1 m³ = 1.000.000 cm³)
– Qhov hnyav (m) = 2 kg
Siv cov qauv ntom ntom:
\[ \rho = \frac{m}{V} = \frac{2 \, \text{kg}}{0,00025 \, \text{m}^3} = 8.000 \, \text{kg/m}^3 \]
Yog li, qhov ceev ntawm cov hlau yog 8.000 kg / m³.
Piv txwv lus nug 5
Lo lus nug:
Ib tug tub ntxhais kawm ntsuas qhov hnyav ntawm ib yam kua thiab pom tias nws yog 250 grams. Yog tias qhov ntim ntawm cov kua yog 200 cm³, qhov ceev ntawm cov kua yog dab tsi hauv g/cm³?
Kev Sib Tham:
Nws paub tias:
– Qhov hnyav (m) = 250 grams
– Ntim (V) = 200 cm³
Siv cov qauv ntom ntom:
\[ \rho = \frac{m}{V} = \frac{250 \, \text{g}}{200 \, \text{cm}^3} = 1,25 \, \text{g/cm}^3 \]
Yog li, qhov ceev ntawm cov kua yog 1,25 g / cm³.
Piv txwv lus nug 6
Lo lus nug:
Ib yam khoom kheej kheej muaj qhov ceev ntawm 7,8 g/cm³ thiab qhov ntim ntawm 500 cm³. Qhov hnyav ntawm yam khoom yog dab tsi?
Kev Sib Tham:
Nws paub tias:
Qhov Ceev (rho) = 7,8 g/cm³
– Ntim (V) = 500 cm³
Siv cov mis hloov pauv kom pom qhov hnyav:
\[ m = \rho \times V = 7,8 \, g/cm^3 \times 500 \, cm^3 = 3.900 \, g \]
Yog li, qhov hnyav ntawm cov khoom yog 3.900 grams lossis 3,9 kg.
Xaus
Qhov ceev yog ib lub tswv yim tseem ceeb hauv kev kawm txog physics uas piav qhia txog kev sib raug zoo ntawm qhov hnyav thiab qhov ntim ntawm ib yam khoom. Cov mis qhia qhov ceev, \( \rho = \frac{m}{V} \), yog siv los xam qhov ceev, qhov hnyav, lossis qhov ntim ntawm ib yam khoom thaum paub ob ntawm peb qhov hloov pauv. Kev nkag siab txog lub tswv yim no yog qhov tseem ceeb rau cov tub ntxhais kawm qib 7 vim nws muab lub hauv paus rau kev kawm cov tswv yim physics nyuaj dua yav tom ntej.
Cov teeb meem piv txwv uas tau muab tso rau hauv tsab xov xwm no yuav pab cov tub ntxhais kawm nkag siab txog yuav ua li cas siv cov mis ntom ntom hauv ntau qhov xwm txheej. Yog tias muaj kev xyaum txaus, cov tub ntxhais kawm yuav npaj tau zoo dua rau kev xeem thiab cov haujlwm uas cuam tshuam nrog lub tswv yim ntawm qhov ntom ntom.
