Lagnever AI English

Speed aur uniform motion

Short mein jawab

Speed kisi cheez dwara ek unit time mein tay ki gayi doori hai: kul doori bhaag kul time. Iski SI unit m/s hai, aur km/h bhi istemaal hota hai. Agar cheez seedhi line pe constant speed se chale, yaani barabar samay mein barabar doori tay kare, to uski gati uniform hai; agar speed badalti rahe, to non-uniform.

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Kaun tez hai?

100 metre ki race mein saare runners ek saath shuru karte hain, par jaldi hi kuch aage nikal jaate hain. Jo runner kisi pal aage hai, usne ek jaise samay mein zyaada doori tay ki hai, isliye wo tez hai. Ek hi doori ki race mein jise sabse kam time lage wo sabse tez hai. Alag-alag doori aur alag-alag time mein chalne waali cheezon ki tulna ke liye ek naap chahiye: speed.

Speed

Speed kisi cheez dwara ek unit time, jaise ek second, ek minute ya ek ghante, mein tay ki gayi doori hai.

Speed = kul tay doori ÷ kul laga time

Speed triangle: upar doori, neeche speed aur time; speed = doori ÷ time, doori = speed × time, time = doori ÷ speed; units m/s aur km/h
Ek formula, teen roop

Kyunki speed doori bhaag time hai, iski SI unit metre per second (m/s) hai. Jab doori kilometre mein aur time ghanton mein ho, to unit kilometre per hour (km/h) hoti hai. Unit badalne ke liye 1 km ko 1000 m aur 1 h ko 3600 s likho, isliye 1 m/s = 3.6 km/h.

Hal kiye gaye udaharan

  • Speed: Swati ka school 3.6 km door hai aur wo 15 min mein cycle se pahunchti hai. Speed = 3.6 km ÷ 15 min = 3600 m ÷ 900 s = 4 m/s.
  • Doori: Raghav ki bus 2 h tak 50 km/h se chalti hai. Doori = speed × time = 50 km/h × 2 h = 100 km.
  • Time: 90 km/h ki train ko 360 km jaana hai. Time = doori ÷ speed = 360 km ÷ 90 km/h = 4 h.

Asli trains ki speed bhi aise hi nikaal sakte ho: railway timetable se do stations ke beech ki doori lo aur use chalne se pahunchne tak ke time se bhaag do.

Average speed aur speedometer

Bus ya train poori yaatra mein shaayad hi ek jaisi speed rakhti hai: wo tez hoti hai, dheemi hoti hai aur rukti hai. Isliye kul doori ÷ kul time se uski average speed milti hai; Class 7 ki book ise bas “speed” kehti hai. Gaadiyon mein speedometer hota hai, jo us pal ki speed km/h mein dikhata hai, aur odometer, jo kul tay doori kilometre mein dikhata hai.

Speedometer ka dial jiski suyi 60 km/h pe hai, aur ab tak ke kilometre dikhata odometer
Abhi ki speed, aur ab tak ki doori

Uniform aur non-uniform motion

Seedhi line pe gati linear motion hai. Station A aur D ke beech seedhi patri pe ek train socho. Wo dheere shuru hoti hai, B tak tez hoti hai, B se C tak constant speed se chalti hai, phir dheemi hokar D pe ruk jaati hai.

Barabar samay ke antar pe bindu: A se B gap badhte hain, B se C barabar rehte hain aur C se D ghatte hain
B aur C ke beech uniform
  • Uniform linear motion: seedhi line pe constant speed se chalna, barabar samay ke antar mein barabar doori tay karna (B se C).
  • Non-uniform linear motion: seedhi line pe badalti speed se chalna, barabar antar mein alag-alag doori tay karna (A se B aur C se D).

Train X aur Y

Bar chart: train X har 10 minute mein 20 km chalti hai; train Y 20, 15, 15, 25, 20 aur 25 km
Kaunsi train uniform motion mein hai?

10:00 se 11:00 AM ke beech train X har 10 minute mein 20 km chalti hai, isliye wo uniform linear motion mein hai. Train Y 20, 15, 15, 25, 20 aur 25 km chalti hai, isliye uski gati non-uniform hai, haalaanki dono ghante mein 120 km chalti hain aur dono ki average speed 120 km/h hai. Lambi dooriyon pe poori tarah uniform gati rozaana zindagi mein kam milti hai; ye ek aadarsh sthiti hai, isiliye hum average speed ke saath kaam karte hain.

Ye kyun zaroori hai

Speed se hum yaatra plan karte hain, runners aur trains ki tulna karte hain, aur speed limit waali sadkon pe surakshit rehte hain. In formulas ka time kaise naapte hain, ye padho time kaise naapte hain mein. Textbook ke sawaalon ke jawab Chapter 8 ke NCERT solutions mein hain; poore chapter ke liye Chapter 8 ke notes.

Practice karo

  1. Ek car 5 s mein 100 m chalti hai. Uski speed hai:

    1. (a) 500 m/s
    2. (b) 20 m/s
    3. (c) 105 m/s
    4. (d) 0.05 m/s
    Jawab dekho

    Jawab: (b) 20 m/s

  2. Ek train 80 km/h se 3 h chalti hai. Wo kitni door jaati hai?

    1. (a) 240 km
    2. (b) 83 km
    3. (c) 26.7 km
    4. (d) 77 km
    Jawab dekho

    Jawab: (a) 240 km

  3. Kaunsa uniform linear motion hai?

    1. (a) Shahar ke traffic mein car
    2. (b) Station se tez hoti train
    3. (c) Seedhe raaste pe har second 10 m chalne waali cheez
    4. (d) Rukti hui ludhakti gend
    Jawab dekho

    Jawab: (c) Seedhe raaste pe har second 10 m chalne waali cheez

  4. 54 km/h ko m/s mein badlo.

    Jawab dekho

    Jawab: 54 km/h = 54 × 1000 m ÷ 3600 s = 15 m/s.

  5. 5 m/s se chalne waale cyclist ko 1.5 km mein kitna time lagega?

    Jawab dekho

    Jawab: 1.5 km = 1500 m. Time = doori ÷ speed = 1500 m ÷ 5 m/s = 300 s, yaani 5 min.

Students ke sawal

Speed kya hai?

Speed kisi cheez dwara ek unit time, jaise ek second ya ek ghante, mein tay ki gayi doori hai. Ise kul tay doori ko kul lage time se bhaag dekar nikaalte hain.

Uniform aur non-uniform motion mein kya fark hai?

Uniform linear motion mein cheez seedhi line pe constant speed se chalti hai aur barabar samay ke antar mein barabar doori tay karti hai. Non-uniform linear motion mein speed badalti rehti hai, isliye barabar antar mein alag-alag doori tay hoti hai.

Average speed kya hai?

Kul doori bhaag kul time, chaahe cheez kabhi tez aur kabhi dheere chali ho. Class 7 ki book mein ‘speed’ ka matlab yahi average speed hai.

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