Ghanatva kya hai? Kuch cheezein kyon tairti aur kuch kyon doobti hain
Short mein jawab
Ghanatva ikai aayatan mein dravyamaan hai: ghanatva = dravyamaan ÷ aayatan. Iski SI unit kg/m³ hai, aur chhoti maatra ke liye g/cm³ ya g/mL istemaal hote hain. Paani lagbhag 1 g/mL hai. Paani se kam ghani cheezein, jaise tel aur barf, us par tairti hain, jabki zyada ghani, jaise patthar aur loha, doob jaati hain.
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Bhaari ya ghana?
Chaawal dhote samay bhoosi tairti hai aur daane doob jaate hain. Paani mein daala tel upar aa jaata hai. Log aksar kehte hain ki tairne wali cheezein halki hoti hain, par lakdi ka bada lattha tairta hai aur chhota kankad doob jaata hai. Ek hi size ki lakdi ki chhadi aur lohe ki chhad sawaal suljha deti hain: loha bahut bhaari lagta hai kyunki usi jagah mein zyada dravyamaan bhara hai. Isi gun ko ghanatva kehte hain.
Socho, bheed bhari bus jismein log ek-doosre se sate hain: zyada ghanatva. Wahi bus kuch musafiron ke saath: kam ghanatva. Paas-paas ugne wale pedon ka jungle ghana kehlaata hai; door-door pedon wala kam ghana.
Formula
Ghanatva kisi padaarth ke ikai aayatan ka dravyamaan hai:
Ghanatva = dravyamaan ÷ aayatan
Ye padaarth ka gun hai, cheez ka nahi, isliye aakaar ya size par nirbhar nahi karta. 120 g aur 60 cm³ ke mitti ke cube ka ghanatva 2 g/cm³ hai, aur patli sheet mein dabaane ke baad bhi 2 g/cm³ hi rehta hai, kyunki na dravyamaan badla na aayatan.
Units aur saapeksh ghanatva
Dravyamaan kilogram mein aur aayatan cubic metre mein ho to SI unit kg/m³ hai. Dravon aur chhoti cheezon ke liye g/mL aur g/cm³ aasaan hain; 1 kg/m³ ka matlab 1 g per litre nikalta hai. Kamre ke taapmaan par 1 mL paani ka dravyamaan lagbhag 1 g hai, isliye 100 mL paani lagbhag 100 g hai, aur paani ka ghanatva lagbhag 1 g/mL hai.
10 cm³ aayatan wale 27 g ke aluminium block ka ghanatva 2.7 g/cm³ hai, yaani wo paani se 2.7 guna ghana hai. Ye anupaat, kisi padaarth ka ghanatva ÷ paani ka ghanatva, uska saapeksh ghanatva hai. Anupaat hone ke kaaran iski koi unit nahi.
Tairna ya doobna?
Jo cheez kisi drav se kam ghani hai wo usmein tairti hai; jo zyada ghani hai wo doobti hai. Tel (lagbhag 0.91 g/mL) paani par tairta hai. 16.4 g aur 5 cm³ ka patthar, 3.28 g/cm³ par, doob jaata hai. Bahut saara namak gholne se paani ghana hota hai, isliye nal ke paani mein doobne wala anda tairne lagta hai. Ghanatva bahut kuch samjhaata hai par sab kuch nahi; aakaar bhi maayne rakhta hai, isiliye halke, khokhle baans ke bede itni achhi tarah tairte hain.
Garmi aur dabaav
Ghanatva aam taur par garam karne se ghatta hai aur thanda karne se badhta hai. Garam kan door-door hote hain, isliye dravyamaan wahi rehte hue aayatan badhta hai, aur dravyamaan ÷ aayatan chhota ho jaata hai. Garam hawa ka ghanatva aas-paas ki thandi hawa se kam hota hai, isliye wo upar uthti hai; hot air balloon aise hi udta hai. Dabaav mukhya roop se gaison par asar karta hai: gas ko dabaane se uske kan paas aate hain aur ghanatva badhta hai, jabki drav aur thos lagbhag nahi badalte.
Barf, aur hamare neeche ki Prithvi
Jamne ke paas paani aam niyam todta hai. Wo 4 °C par sabse ghana hota hai, aur 0 °C par barf bante samay uske kan zyada jagah gherte hain. Isliye barf paani se kam ghani hoti hai aur tairti hai, ek dhakkan ki tarah jo sabse thandi sardiyon mein bhi neeche ka paani machhliyon ke liye drav rakhta hai.
Prithvi bhi ghanatva ke hisaab se parton mein bani hai. Crust sabse halki parat hai; neeche upper aur lower mantle se hote hue liquid outer core aur solid inner core tak dabaav aur taapmaan badhte jaate hain aur padaarth aur kasa hota jaata hai.
Khud ghanatva nikaalne ke liye do maap chahiye; dekho dravyamaan aur aayatan kaise naapein. Ghulansheelta kya hai, Chapter 9 ke notes aur NCERT solutions bhi padho.
Practice karo
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Patthar ki ek moorti ka dravyamaan 225 g aur aayatan 90 cm³ hai. Uska ghanatva hai:
Jawab dekho
Jawab: (b) 2.5 g/cm³
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Saapeksh ghanatva ki:
Jawab dekho
Jawab: (c) koi unit nahi
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Kisi padaarth ko garam karne par uska ghanatva aam taur par:
Jawab dekho
Jawab: (b) ghatta hai
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Tel ke pack par 1 litre likha hai par sirf 910 g. Isse kya pata chalta hai?
Jawab dekho
Jawab: 1 litre paani ka dravyamaan lagbhag 1000 g hota hai, isliye utne hi aayatan ka tel halka hai. Tel ka ghanatva lagbhag 0.91 g/mL hai, paani ke 1 g/mL se kam, isliye tel paani par tairta hai.
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Dabaav hawa ka ghanatva paani se kahin zyada kyon badalta hai?
Jawab dekho
Jawab: Gas ke kan door-door hote hain, isliye dabaane par ve paas aa jaate hain, aayatan ghatta hai aur ghanatva badhta hai. Drav aur thos ke kan pehle se paas-paas hote hain, isliye dabaav se unka aayatan ya ghanatva lagbhag nahi badalta.
Students ke sawal
Aasaan shabdon mein ghanatva kya hai?
Ghanatva batata hai ki kisi jagah mein padaarth kitna kasa hua hai. Bheed bhari bus mein ek hi jagah mein bahut log hote hain, isliye wo ghani hai; kuch hi musafiron wali bus nahi. Isi tarah loha har cubic centimetre mein lakdi se zyada dravyamaan rakhta hai.
Ghanatva ki SI unit kya hai?
Kilogram per cubic metre (kg/m³), kyunki dravyamaan kilogram mein aur aayatan cubic metre mein naapa jaata hai. Chhoti cheezon aur dravon ke liye gram per cubic centimetre (g/cm³) ya gram per millilitre (g/mL) zyada suvidhajanak hai.
Barf paani par kyon tairti hai?
Paani 4 °C par sabse ghana hota hai. 0 °C par jamte samay uske kan aise jamte hain ki zyada jagah gherte hain. Wahi dravyamaan ab bade aayatan mein hota hai, isliye barf drav paani se kam ghani hoti hai aur upar tairti hai.
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