Force And Pressure Class 8 Chapter 7

Pressure Force and Area

Jab tap men se paani ziada speed se nikalta ha to ham kehte hain ke paani ka presssure ziada ha. Agar ham apne hath ke hatheli paani ki dhar ke neeechay rakhen to ham apne hath per ek force (Dabaao) mehsoos kerte hain. Hamare hath ki hatheli per amal kerny wali is amoodi force ko pressure kehte han.

pas pressure ki tareef yun ki ja sakti ha. “kisi chez ki satah ke unit area per amoodan amal kerne wali force”.

Hisabi tor per pressure ki tareef yun ki ja skati ha.

Pressure =  Force/Area

Pressure ko angrezi men P, Force ko F aur Area ko A se zahir kiya jata ha.

Agar mukhtalif area ke ajsam per ek hi jitini force lagai jaye to  chote area per pressure ziada ho ga jabke bare area per pressure kam ho ga. Isi tarahn jab ek hi area ke ajsam per mukhatlif forces lagai jayen to bare force ziada pressure dale gi ba nisbat chote force.

Pressure Ke Units (Nm-2) ya Pascal (Pa)

Pressure ek physical mikdar ha jis ke units force aur area ke units ki shakal me zahir kye ja sakte han. Force ka unit Newton (N) ha. Aur area ka unit Muraba meter ha (m2) ha. Choonke pressure unit area per force ha is lye iska unit newton fi puraba meter (Nm-2) ha. Ye pressure ka SI unit ha. Ise pascal bhi kehte han. Pascal ko Pa se zahir kya jata ha.

Water Pressure

Hamara mushahida ha ke water tank se hamare ghar ki nichli manzal per toonti ke zarye ane wale paani ki speed ooper wali mazil per toonti se  aane wale paani ki speed se ziada hoti ha. Darasal tank men bhara jua paani is ki dewaaron per pressure daalta ha. Toonti se aane wale paani ki speed tank men paani ke pressure per munhasir ha. Lehaza toonti ke paani ka pressure zameen se water tank ki oonchai per bhi  munhasir ha. yahi waja ha ke water tank akhri manzil ki chat per rakhe jate han. Pani ka pressure pipes ke zarye toonti ko mutakil hota ha.

Liquid Pressure In Closed Containers

Bartanon men band mayaat aur fluids (Sial ashya jin men mayaat aur gases shamil han) tamam atraaf men masavi pressure daalti han. Agar kisi band bartan men band sial shay per pressure dala jaye to wo tamam atraf men barabar muntakil ho jata ha. Ye haqeeqat sab se pehle pascal ne daryaft ki aur ye pascal ka qanoon kehlata ha. Pascal ka kanoon sirf bartan men band sial per lagoo hota ha.

Science ki wo branc jo peipes ke zariye fluid pressure ki makanki force ke taur per muntakli se taluq rakhti ha Hydraulics kehlati ha. is kisam ke systems aksar choti force ki madad se bare force muhaya kerne ke lye istamal kye jate ha.

Applications of Pascal’s Law , Hydraulic System

Jack System

Is system men chote piston per ek choti force F1 lagai gai ha jis se oil per pressure P parta ha. Pressure P pipes ke zarye ek boht bare cylinder ko muntakil ho jata ha jis men piston fit k hota ha. Choonke is piston ka area bht bara ha lehaza is bare piston per pressure P ki waja se ek bht bari force paida hoti ha  jo ke bhari chez maslan car waghera ko ooper uthane ke lye istamal men lagir ja sakti ha.

Valves V1 aur V2 oil ko biltarteeb oil tank aur chote cylinder men wapis jane se rokte han taake bhari load ooper utha rahe. Jab oil ka stopper khola jata ha to bare cylinder ka oil wapis oil tank men chala jata ha aur load neechay aa jata ha.

Hydraulic Brake System

Car ke andar brake system, hydraulic system ki ek aur aaam misall ha. Ye ek pipe aur do cylinders per mushtamil hota ha. Is men ek khass kisam ke oil bhara jata ja jise Brake Oil kehte ha. Pipe ke ek sire per chota cylinder hota ha jis men piston fit kya jata ha aur use Master cylinder kehte han.

Is ka chota piston brake ke padal ke sath munsalik hota ha. Pipe ke doosre sire per bara cylinder hota ha jis men bara piston fit kya hota ha . Ise slave sylinder kehte han . Jab braake padal per ek choti force laga ker chote piston ko master cylinder men dhakela jata ha to is tarahn oil men paida hone wala pressure baghair zaaya hue slave cyli8nder ko mutakil kya jata ha.

Slave cylinder  ka bara piston ek bari force se bahir ko dhakela jata ha. Tab ye brake pad ko bahir ki taraf dhakelta ha taake ye chalte hue wheel ki disk ke sathe ragar khaye. Is tarhn ek bare friction force paida hoti ha jo chalte hue wheel ko rok deti ha.

Gas Pressure in a Container

Kisi bartan men gas ke molecules tamam atraaf men musalsal harkat kerte rehte han. Apni harkat ke doran men wo har waqt ek doosre se aur bartan ki dewaaron se takrate rehte han. Gas ke molecules jab bartan ki dewaaron se takrate han to un per force lagate han aur is tarhn bartan ki dewaaron per pressure dalte han.

Agar gas ki utni hi mikdar ke lye bartan ka volume kam ker dya jaye to molecules ke darmyan fasla bhi kam hojata ha aur bartan ki dewaaron ke sathe molecules ka takraao barh jata ha. Nateegah ke tor per pressure barh jata ha.