PhysicsPushan · Class 9-10
Parachute: gravity se jeetna nahin, usse samjhauta karna
Gravity toh parachute par bhi utni hi lagti hai, phir woh aadmi dheere kyun utarta hai?
Socho pehle… phir dekho jawab
Kyunki girte waqt hawa oopar ki taraf dhakka deti hai — isse air resistance ya drag kehte hain. Parachute ka bada area bahut saari hawa rokta hai, drag badh jaata hai, aur jaldi hi drag aur weight barabar ho jaate hain. Net force zero, toh speed badhna band.
NCERT mein padha hai ki free fall mein har cheez g, yaani lagbhag 9.8 m/s² se tez hoti jaati hai. Par wahan hawa ko ignore kiya jaata hai. Asli duniya mein hawa hai, aur woh girti cheez ke raaste mein aati hai.
Drag do cheezon par bahut depend karta hai: speed aur saamne wala area. Jitni tez girogi, utna zyada drag. Ek point par drag = weight ho jaata hai. Ab Newton ka pehla niyam kaam karta hai: net force zero hai toh velocity constant rahegi. Isi steady speed ko terminal velocity kehte hain.
Parachute khulte hi area achanak bahut bada ho jaata hai, toh terminal velocity bahut kam ho jaati hai — itni ki zameen par safe utra ja sake. Spacecraft ke capsules mein pehle chhote drogue parachute khulte hain jo speed kam karte hain aur capsule ko stable karte hain, phir bade main parachute. Ek saath sab khol do toh jhatka bahut zyada hoga.
Ghar pe try karo
Do ek jaise A4 kaagaz lo. Ek ko chapta rakho, doosre ko kas ke gend jaisa murod do. Dono ko ek hi oonchai se saath chhodo. Mass same hai, phir bhi gend pehle girti hai. Ab socho: farq kis cheez ka tha?
Wow!
Parachute gravity ko band nahin karta — bas hawa ko itna bada 'haath' deta hai ki woh gravity ke barabar khinch sake.
3 sawaal
- Parachute khulne ke baad speed badhna kyun ruk jaata hai?
Jawab dekho
Drag aur weight barabar hokar net force zero kar dete hain. Net force zero ho toh Newton ke pehle niyam se velocity constant rehti hai — yahi terminal velocity hai.
- Chapta kaagaz aur murda hua kaagaz (same mass) — chapta der se kyun girta hai?
Jawab dekho
Uska area zyada hai, toh drag zyada. Mass aur gravity same hain; farq sirf saamne ke area ka hai jo drag badhata hai.
- NCERT ke free fall wale sawaalon mein kaunsi cheez ignore ki jaati hai?
Jawab dekho
Air resistance. Free fall ka ideal model hawa ko ignore karta hai, isliye wahan sab cheezein saath girti hain.
NCERT se jodo: NCERT Class 9 Science — force aur laws of motion; gravitation aur free fall