Questions: Pressure, winds, storms and cyclones

Q1. Define pressure, write its formula and state its SI unit.

Answer (English): Pressure is the force acting on a unit area of a surface, with the force perpendicular to that surface. It is calculated as pressure equals force divided by area, written as P = F / A. The SI unit of pressure is the newton per square metre (N/m²), which is also called the pascal (Pa). For the same force, a smaller area gives a larger pressure.

Hinglish: Pressure woh force hai jo surface ke unit area par lagta hai, aur force surface ke perpendicular hota hai. Formula: P = F / A. SI unit newton per square metre (N/m²) yaani pascal (Pa) hai. Same force ke liye chhota area zyada pressure deta hai.

Q2. Why is a bag with broad straps more comfortable than one with narrow straps?

Answer (English): Both bags may have the same weight, but the area over which that weight acts is different. A narrow strap presses the load on a small area of the shoulder, so the pressure is large and the shoulder hurts. A broad strap spreads the same load over a larger area, so the pressure is smaller and the bag feels more comfortable. The same reasoning explains why a bucket with a broad handle is easier to carry.

Hinglish: Dono bags ka weight same ho sakta hai, par weight jis area par lagta hai woh alag hota hai. Patli strap chhote area par load daalti hai, isliye pressure zyada hota hai aur kandha dukhta hai. Broad strap same load ko bade area par phaila deti hai, isliye pressure kam aur bag comfortable lagta hai. Bucket ka broad handle bhi isi wajah se aasan lagta hai.

Q3. Why does a sharp knife cut better than a blunt one?

Answer (English): A sharp knife has a very thin edge, so the force of the hand acts on a very small area. Since pressure is force divided by area, the same force produces a much larger pressure on the food, and the edge cuts through easily. A blunt knife has a wider edge, so the force is spread over a larger area and the pressure is smaller. A pointed nail works the same way when it is struck.

Hinglish: Tez knife ka edge bahut patla hota hai, isliye haath ka force bahut chhote area par lagta hai. Pressure = force ÷ area, isliye same force se bahut zyada pressure banta hai aur knife aasani se kaat leti hai. Blunt knife ka edge chaura hota hai, force zyada area par phailta hai aur pressure kam hota hai. Nail ka pointed end bhi isi tarah kaam karta hai.

Q4. Why does liquid pressure depend on the height of the liquid column? Why are water tanks placed high?

Answer (English): In the chapter's activity, two pipes of different diameters are filled with water to the same height, and the balloons at the bottom bulge equally. The amounts of water differ, but the pressure is the same, which shows that pressure depends on the height of the column rather than the weight of the liquid. Adding more water to a pipe increases the height and the bulge increases too. Water tanks are placed high so that the tall column produces enough pressure for a strong flow from taps, and a lower-floor tap gets more pressure than a higher-floor tap.

Hinglish: Activity mein do alag diameter ke pipes mein paani same height tak bhara, aur neeche ke balloons barabar phule. Paani ki matra alag thi par pressure same, isliye pressure height par depend karta hai, weight par nahi. Zyada paani se height badhti hai to bulge bhi badhta hai. Tanki upar lagti hai taaki tall column se taps mein accha pressure mile; neeche wale floor ke tap ko zyada pressure milta hai.

Q5. How do we know that liquids exert pressure on the sides of a container? How does a dam use this idea?

Answer (English): If small holes are made at the same height around the bottom of a plastic bottle and the bottle is filled with water, water flows out from every hole. This shows that the liquid pushes on the walls of its container, so liquids exert pressure sideways as well as downwards. A dam applies the same idea: water presses horizontally on the wall, and the pressure near the base is much larger because of the taller column above, so the base of the dam is made broad to withstand it.

Hinglish: Bottle ke neeche same height par chaaron taraf chhote holes bana kar paani bharo, to har hole se paani nikalta hai. Iska matlab liquid container ki walls par bhi pressure deta hai, sirf neeche nahi. Dam isi idea par banta hai: paani wall par horizontally pressure deta hai, aur neeche paas pressure zyada hota hai kyunki upar column lamba hai, isliye dam ka base chaura banaya jaata hai.

Q6. How does a rubber sucker stay on a surface, and how large is atmospheric pressure?

Answer (English): Pressing the sucker pushes most of the air out from under its cup, so the pressure inside the cup becomes lower than the air pressure outside. The higher outside pressure holds the sucker against the surface, and pulling it off needs a force large enough to overcome the difference. Atmospheric pressure is large: the air above an area of 15 cm by 15 cm presses with a force close to 2250 N, about the weight of a 225 kg object. We are not crushed because fluids inside our body push outwards with nearly the same pressure.

Hinglish: Sucker dabane se cup ke neeche ki zyadatar hawa nikal jaati hai, isliye andar ka pressure bahar se kam ho jaata hai. Bahar ka zyada pressure sucker ko surface par pakad leta hai; nikaalne ke liye pressure difference se zyada force chahiye. Atmospheric pressure bada hai: 15 cm × 15 cm area par hawa ka force kareeb 2250 N hota hai, jo 225 kg ke weight ke barabar hai. Hum isliye nahi dabte kyunki body ke andar ke fluids bhi kareeb utna hi pressure bahar ki taraf dete hain.

Q7. How are winds formed? Explain sea breeze and land breeze.

Answer (English): Winds form because air moves from a region of higher pressure to one of lower pressure. During the day, land heats faster than water. Warm air over the land rises, creating low pressure near the ground, and cooler air from the sea moves in to fill the gap; this is the sea breeze. At night, the sea stays warmer, so warm air rises over the water and low pressure forms there; air then moves from the land towards the sea, which is the land breeze.

Hinglish: Hawa high pressure se low pressure ki taraf chalti hai, isi se wind banti hai. Din mein zameen paani se jaldi garam hoti hai: zameen ke upar garam hawa uthti hai aur neeche low pressure ban jaata hai, samundar se thandi hawa aa jaati hai, ise sea breeze kehte hain. Raat ko samundar garam rehta hai, wahan low pressure banta hai, aur hawa zameen se samundar ki taraf chalti hai, ise land breeze kehte hain.

Q8. Why are high-speed winds accompanied by lower pressure, and why can they blow roofs off?

Answer (English): In the two-balloon activity, blowing air through the gap makes the balloons move towards each other. The fast-moving air creates low pressure between them, and the higher pressure outside pushes them together. Blowing harder increases the effect. When fast wind blows over a roof, low pressure forms above the roof while the pressure below stays higher, so a weak roof can be lifted and blown away. Keeping doors and windows open reduces the pressure difference and lowers the risk.

Hinglish: Do balloon activity mein beech mein hawa phooko to balloons ek doosre ki taraf aate hain: tez hawa se beech mein low pressure ban jaata hai aur bahar ka zyada pressure unhe paas dhakelta hai. Zyada zor se phookne par effect badhta hai. Tez hawa chhat ke upar se guzre to upar low pressure aur neeche zyada pressure ho jaata hai, isliye kamzor chhat ud sakti hai. Darwaze-khidkiyan khuli rakhne se pressure ka farak kam hota hai.

Q9. How do thunderstorms and lightning form, and what precautions should be taken during lightning?

Answer (English): Warm, moist air rises, and cooler air rushes in to take its place, setting up a circulation. The rising air cools, its vapour condenses into clouds, and the droplets fall as rain, hail or snow, producing a storm. Strong upward and downward winds rub ice particles and water droplets together, separating positive and negative charges in the cloud; the lower negative part makes the ground positive. When the air's insulation breaks down, the charges flow suddenly as lightning, and the heated, expanding air produces thunder. During lightning, avoid tall objects, crouch in a low open area, do not lie flat, avoid metal umbrellas, get out of water, and stay inside a bus or car if possible.

Hinglish: Garam-nam hawa upar uthti hai aur thandi hawa uski jagah leti hai, isse circulation banta hai. Upar jaakar hawa thandi hoti hai, vapour baadal banta hai, aur boondein baarish/hail/snow ki tarah girti hain, isse storm banta hai. Tez upar-neeche ki hawa ice particles aur boondon ko rub karti hai, jisse cloud mein positive-negative charges alag hote hain; neeche ka negative part zameen ko positive banata hai. Air ki insulation tootne par charges achanak flow karte hain, wahi lightning hai, aur garam hawa phailne se thunder hota hai. Lightning mein unchi cheezon se door raho, khuli neevi jagah par jhuk kar baitho, let kar mat so, metal umbrella mat use karo, paani se bahar aao, aur bus/car mein raho.

Q10. How does a cyclone form, what is its eye, and how should people prepare for it?

Answer (English): A cyclone forms over warm ocean water. Warm, moist air rises, and when its vapour condenses, heat is released that warms the air further and makes it rise faster, creating a very low-pressure region. Surrounding air rushes in, the Earth's rotation makes it spin, and the result is a large spinning system of clouds, wind and rain. The eye is the centre of lowest pressure, where winds are calm, while strong winds and heavy rain surround it. Cyclones can flood coasts with a storm surge, contaminate water and block roads, so people should follow IMD alerts and weather reports, keep an emergency kit and move to a cyclone shelter when told.

Hinglish: Cyclone garam samundar ke paani ke upar banta hai. Garam-nam hawa uthti hai; vapour condense hone par heat nikalti hai jo hawa ko aur garam karke upar uthaati hai, jisse bahut low pressure ban jaata hai. Aas-paas ki hawa andar aati hai, Earth ke rotation se ghoomti hai, aur clouds-wind-rain ka bada spinning system ban jaata hai. Eye centre hota hai jahan pressure sabse kam aur hawa shaant hoti hai, par uske chaaron taraf tez hawa aur baarish hoti hai. Cyclone se storm surge, paani ka contamination aur roads block ho sakte hain, isliye IMD alerts/weather reports follow karo, emergency kit rakho aur shelter chale jao.

The quick check below has five multiple choice questions on pressure, liquid pressure, air pressure and cyclones. Each one comes with a short explanation, so take the quiz and see which topics need another read.