PhysicsPushan · Class 9-10
p = hρg: gehrai ka dabaav, aur 10 metre ki hawa wali seema
Kabhi socha hai ki gaon ka haath wala pump (suction pump) bahut gehre kuein se paani kyun nahi kheench paata? Kya pump kamzor hai, ya physics ki koi seema hai?
Socho pehle… phir dekho jawab
Suction pump paani ko 'kheenchta' nahi; woh upar ki hawa ka dabaav kam karta hai, aur bahar ka vayumandaliya dabaav paani ko upar dhakelta hai. Vayumandaliya dabaav sirf lagbhag 10 m paani ke stambh ke barabar hai — usse upar dhakelne ki taakat hi nahi.
Thrust aur pressure: thrust = satah par perpendicular bal (N); pressure = thrust ÷ area (Pa = N/m²). Wahi thrust chhote area par zyada pressure deta hai.
Derivation: area A, gehrai h ka paani ka stambh. Uska mass = ρ × A × h, wazan = ρAhg. Neeche pressure = wazan ÷ A = hρg. Pressure sirf gehrai (h), density (ρ) aur g par tika hai — bartan ki shape ya kul paani par nahi. Ek gehrai par har disha mein barabar.
Vayumandaliya dabaav ≈ 1.01 × 10⁵ Pa. hρg = 1.01 × 10⁵ rakho (ρ = 1000 kg/m³, g ≈ 9.8 m/s²) toh h ≈ 10.3 m. Isliye suction pump siddhaant mein lagbhag 10 m se upar paani nahi utha sakta; asal mein leakage aur ghisaav se aur kam. Gehre paani ke liye neeche paani mein laga pump (submersible) chahiye, jo dhakel kar upar bhejta hai.
Cause-effect chain: gehrai badhi, phir upar ke paani ka wazan badha, phir hρg badha, isliye neeche ki deewar par zyada dhakka — yahi baandh-design ka pehla niyam hai.
Humne kya kiya :- hρg ko paani ke stambh ke wazan se nikaala aur vayumandaliya dabaav ko 10 m paani mein badla.
Isse kya hua :- Samjhe ki haath-pump ki seema physics ki hai, aur gehrai ke saath dabaav seedhe (linearly) badhta hai.
Ghar pe try karo
Teen chhed wali bottle (chhed bade karein) mein chhedon ki oonchai paani ki satah se naapo (h1, h2, h3), phir dhaar ki doori naapo. Graph banao: gehrai (x) vs doori (y). Gehrai badhne par doori kaise badhti hai? Paani paudhon mein daal do.
Wow!
Har 10 metre gehre paani mein dabaav lagbhag ek vayumandal badhta hai — isliye 6,000 m par lagbhag 600 vayumandal!
3 sawaal
- Gehrai h par liquid ka dabaav (hawa ka dabaav chhod kar) kitna hota hai?
Jawab dekho
hρg. Stambh ka wazan ρAhg ÷ area A = hρg.
- Vayumandaliya dabaav lagbhag kitne metre paani ke stambh ke barabar hai?
Jawab dekho
Lagbhag 10 m. 1.01 × 10⁵ Pa = hρg se h ≈ 10.3 m paani.
- Liquid ka dabaav kis par NAHI tika?
Jawab dekho
Bartan ki shape. p = hρg; bartan ki shape ya kul paani ka dabaav par asar nahi.
NCERT se jodo: NCERT Class 9 Science — gravitation: thrust aur pressure, liquid ka dabaav; Class 11 Physics — fluids (idea in words)