Dravyamaan aur aayatan kaise naapein
Short mein jawab
Dravyamaan balance par naapa jaata hai: digital balance ko zero karo, watch glass rakho, tare dabao, phir cheez rakho. Drav ka aayatan measuring cylinder mein, meniscus ke star par aankh rakhkar, padha jaata hai. Cuboid ka aayatan lambaai × chaudaai × oonchaai hai; be-dhang thos ka aayatan use paani mein utaarne par star ki badhat hai.
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Dono kyon naapein?
Ghanatva dravyamaan ÷ aayatan hai, isliye kisi bhi cheez ka ghanatva, patthar se lekar ek chammach tel tak, nikaalne ke liye do dhyaan se kiye gaye maap chahiye. Chapter 9 Activities 9.3 se 9.7 mein dono ke tareeke batata hai.
Digital balance par dravyamaan
Dravyamaan kisi cheez mein padaarth ki maatra hai. Ise balance se naapte hain, aur digital weighing balance ise jaldi kar deta hai (Activity 9.3):
- Balance chalu karo aur display dekho. Wo zero dikhaana chahiye; nahi to tare (reset) button dabao.
- Pan par saaf, sookha watch glass ya butter paper rakho aur reading dekho.
- Tare phir dabao, taaki watch glass rakhe hue display zero par aa jaaye.
- Cheez, jaise patthar, watch glass par rakho.
- Display padho: yahi patthar ka dravyamaan hai, jaise 16.400 g.
Drav ke liye watch glass ki jagah beaker lo, use tare karo, aur drav daalo.
Rozmarra ki bolchaal mein “dravyamaan” aur “bhaar” ek hi matlab mein bole jaate hain, par science mein ye alag hain. Dravyamaan gram aur kilogram mein naapa jaata hai. Bhaar wo bal hai jisse Prithvi kisi cheez ko kheenchti hai, newton mein. Do pan wale balance ko chhodkar zyaadatar balance asal mein bhaar mehsoos karte hain, par unke scale aise bane hote hain ki gram ya kilogram mein dravyamaan dikhaayein.
Drav ka aayatan
Aayatan wo jagah hai jo koi cheez gherti hai. SI unit cubic metre (m³) hai; chhote aayatan ke liye cubic decimetre (dm³) ya cubic centimetre (cm³, jise cc bhi kehte hain). Ek litre 1 dm³ ke barabar hai aur ek millilitre 1 cm³ ke, isliye chhaachh ke 200 mL pack mein 200 cm³ hai.
Measuring cylinder ek patli, paardarshi nali hai, ek sire se band, jiski deewar par aayatan ke nishaan hote hain. Ye 5, 10, 25, 50, 100 aur 250 mL jaise size mein aate hain. Kisi ki sabse chhoti reading nikaalne ke liye (Activity 9.4) do number wale nishaan lo, jaise 10 mL aur 20 mL, aur antar ko unke beech ke chhote bhaagon ki sankhya se bhaag do: 100 mL cylinder ke liye 10 mL ÷ 10 = 1 mL. Chhote cylinder aksar 0.1 mL tak, 250 mL wala 2 mL tak aur 500 mL wala 5 mL tak padhte hain. Isliye zaroorat ke aayatan ke paas ka size chuno: 70 mL ke liye 100 mL ka cylinder ek hi baar mein aur 1 mL tak naap deta hai.
Meniscus
50 mL paani naapne ke liye (Activity 9.5) cylinder ko samtal jagah par rakho, nishaan tak dheere-dheere paani daalo, aur dropper se theek karo. Paani ki sateh mud jaati hai; is mod ko meniscus kehte hain. Aankhen iske star par rakho aur paani aur doosre rangheen (colourless) dravon ke liye mod ke nichle hisse wala nishaan padho. Rangeen dravon ke liye meniscus ka upari hissa padho.
Thos ka aayatan
Niyamit aakaar wala thos aasaan hai (Activity 9.6). Cuboid ko scale se naapo aur guna karo: 25 cm lambi, 18 cm chaudi aur 2 cm moti notebook ka aayatan 25 × 18 × 2 = 900 cm³ hai.
Patthar ki koi seedhi bhujaayein nahi hoti, isliye visthaapan lagao (Activity 9.7). Measuring cylinder mein ek tay star tak paani daalo, jaise 50 mL. Patthar ko dhaage se baandho aur dheere se andar utaaro; star badhta hai, jaise 55 mL tak. Badhat, 55 − 50 = 5 mL, hataaye gaye paani ka aayatan hai, jo patthar ke aayatan, 5 cm³, ke barabar hai. Dhaatu ki chaabi se bhi aazmaao.
Dono ko jodna
Patthar ke dravyamaan (16.400 g) aur aayatan (5 cm³) se ghanatva = 16.4 ÷ 5 = 3.28 g/cm³. Ye paani ke 1 g/cm³ se zyada hai, isliye patthar doobta hai. Aur padho ghanatva kya hai aur ghulansheelta kya hai, ya Chapter 9 ke notes aur NCERT solutions dekho.
Practice karo
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Digital balance ka tare button kis kaam aata hai?
Jawab dekho
Jawab: (b) reading ko wapas zero par laane ke
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Measuring cylinder mein paani ki reading li jaati hai:
Jawab dekho
Jawab: (b) meniscus ke nichle hisse par
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Patthar utaarne par cylinder ka paani 50 mL se 55 mL ho jaata hai. Patthar ka aayatan hai:
Jawab dekho
Jawab: (a) 5 cm³
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25 cm lambi, 18 cm chaudi aur 2 cm moti notebook ka aayatan nikaalo.
Jawab dekho
Jawab: Aayatan = lambaai × chaudaai × oonchaai = 25 cm × 18 cm × 2 cm = 900 cm³.
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70 mL paani naapne ke liye kaun sa cylinder chuna jaaye: 50 mL, 100 mL ya 500 mL? Kyon?
Jawab dekho
Jawab: 100 mL wala. 50 mL wale se do baar naapna padega, aur 500 mL wale ki sabse chhoti reading 5 mL hai, isliye wo kam sateek hai. 100 mL wala 70 mL ek hi baar mein, 1 mL tak sahi naapta hai.
Students ke sawal
Dravyamaan aur bhaar mein kya antar hai?
Dravyamaan kisi cheez mein padaarth ki maatra hai, gram ya kilogram mein. Bhaar wo bal hai jisse Prithvi us cheez ko kheenchti hai, newton mein. Do pan wale balance ko chhodkar zyaadatar balance asal mein bhaar mehsoos karte hain, par unki reading dravyamaan ki units, gram ya kilogram, mein di jaati hai.
Patthar jaisi be-dhang cheez ka aayatan kaise nikaalein?
Visthaapan vidhi lagao. Measuring cylinder mein ek tay star tak paani bharo, jaise 50 mL, patthar ko dhaage se baandhkar dheere se utaaro, aur naya star likho, jaise 55 mL. Antar, 5 mL, patthar ka aayatan hai, jo thos ke liye 5 cm³ likha jaata hai.
Measuring cylinder lambe aur patle kyon hote hain?
Patli nali mein aayatan ka chhota sa badlaav bhi drav ki oonchaai mein saaf dikhta hai, isliye nishaan door-door lagte hain aur zyada sateekta se padhe jaate hain. Chaude, chhote bartan mein wahi badlaav star ko mushkil se hilaata.
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