Define gravitational potential energy
Scenario
Ek patthar zameen par pada hai toh koi khatra nahi. Par wahi patthar 5th floor ki balcony ke edge par rakha ho toh dar lagta hai ki gir na jaaye.
Height par hone ki wajah se patthar ke andar aisi kaunsi takat aa gayi hai?
Mental model
Height = Stored Energy. Jab aap kisi cheez ko upar uthate ho, to aapka kiya gaya kaam usme gravity ki wajah se 'store' ho jata hai.
Gravitational potential energy wo energy hai jo kisi object ke paas sirf isliye hoti hai kyunki uski position zameen se upar hai. Jab aap block uthate ho to gravity ke against work karte ho, wo work waste nahi hota, block mein store ho jata hai.
Explanation
Energy sirf tab nahi hoti jab koi object ghoom raha ho ya chal raha ho. Kai baar position ya state ki wajah se bhi energy store ho jati hai. Ise Potential Energy kehte hain. Iska ek khaas roop hai Gravitational Potential Energy.
Jab aap kisi object ko ground (zameen) se certain height tak upar uthate ho, aapko ek force lagana padta hai jo gravity (jo object ko niche khich rahi hai) ke barabar ho. Aapne upward displacement kiya gravity ke against, toh aapne ek work kiya.
Ye work done kahi jadu se gaayab nahi hota. Ye us object ke andar store ho jata hai as gravitational potential energy. Jaise hi aap us object ko drop karte ho, wo stored energy release hoti hai aur turant Kinetic Energy (motion) mein badal jati hai. Jitna ooncha aap uthaoge, utna zyada work karoge, aur utni hi zyada usme potential energy store hogi. Ground level par hum is energy ko zero maante hain reference ke liye.
Worked example
Problem: Why does a raised hammer have energy even if it is not moving at the top point?
- Energy object ki position (height) ki wajah se ho sakti hai.
- Hammer ko uthane mein work kiya gaya jo usme store ho gaya.
Answer: It has stored gravitational potential energy due to its raised position.
Problem: A heavy stone at the edge of a cliff has the potential to do a lot of damage if it falls. What kind of energy does it possess?
- Stone abhi cliff par hai (zameen se bahut height par).
- Height aur gravity ki wajah se isme potential energy hai.
Answer: Gravitational potential energy
Key points
- Stored Energy: Energy stored in an object due to its position above the ground is called gravitational potential energy.
- Work Against Gravity: It is equal to the work done on the object against gravity in moving it to a certain height.
Common mistakes
- Assuming energy means motion: Kayi log puchte hain 'Agar block hila hi nahi toh energy kahan se aayi?' Hamesha yaad rakhna, ek stretched rubber band aur height par rakha block dono ruke hue hain, fir bhi unme stored potential energy hoti hai.
Recall questions
- What is the energy possessed by an object due to its height above ground called?
- What is the reference level usually chosen to measure gravitational potential energy?
- Does potential energy depend on the path taken to raise the object?
Questions & answers
What is the energy possessed by an object due to its change in position or shape?
Potential energy.
Approach: Position relates to gravitational potential energy, shape relates to elastic potential energy. Both fall under the broader category.
Does a stretched bow string have energy? If yes, what kind?
Yes, it has potential energy (elastic potential energy).
Approach: Due to the change in its shape.
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