Define power
Scenario
Ek uncle 3rd floor par sidhiyon se 5 minute mein pahuchte hain. Wahi unka chota beta daud kar 1 minute mein chadh jata hai.
Dono ne apni body (mass) ko utni hi height par le jaane mein same 'work' kiya, par difference kis baat ka hai?
Mental model
Work wahi, par time alag. Power = Speed of doing work.
Ek hi kaam koi jaldi karta hai toh uski Power zyada hai. Power physics mein bas yahi measure karti hai ki aap kitni tezi se energy use kar rahe ho ya work kar rahe ho.
Explanation
Physics mein work karna hi sab kuch nahi hota. Kitne time mein work kiya ja raha hai, ye bhi utna hi zaroori hai. Yahan par ek naya concept aata hai jise Power kehte hain.
Power is defined as the rate of doing work, ya fir rate of transfer of energy. Simple bhasha mein, kaam karne ki raftaar hi power hai. Iska mathematical equation bahut hi straightforward hai: `Power = Work done / Time taken` yaani `P = W/t`.
Iska matlab, agar work fixed hai, aur aap time kam loge (tezi se kaam karoge), toh apki power zyada nikalegi. Kyunki Power work aur time ka ratio hai, iska standard unit Joule/second (J/s) hota hai. Is J/s ko ek special naam diya gaya hai, 'Watt' (symbol: W), James Watt (jinhone steam engine improve kiya tha) ke naam par.
1 Watt (1 W) ki power tab maani jati hai jab koi machine 1 second mein 1 Joule (1 J) ka work karti hai (ya energy consume karti hai).
Worked example
Problem: A machine does a work of 100 J in 20 s. What is its power?
- Work aur time diya gaya hai.
- Power ko 'work divided by time' se calculate karte hain.
- Simple division karo.
Answer: 5 W
Problem: An athlete uses 6000 J of energy in a 10 second sprint. What is his power output?
- Energy use karna matlab utna work karna.
- Power is rate of energy transfer.
- Calculate karke Watt mein likho.
Answer: 600 W
Key points
- Definition of Power: Power is the rate of doing work or the rate of transfer of energy.
- SI Unit: The SI unit of power is Watt (W). 1 W = 1 J/s.
Common mistakes
- Confusing 'W' for Work and Watt: Formula (P = W/t) mein 'W' ka matlab Work done hai. Lekin unit likhte time jo 100 W likhte hain, wo Watt hai. Dono ko aapas mein mix mat karna.
Recall questions
- What is the formula for power?
- What is the unit of power?
- If two boys do the same amount of work but boy A takes less time than boy B, who has more power?
- Is power a scalar or vector quantity?
Questions & answers
Define 1 watt of power.
1 watt is the power of an agent which does work at the rate of 1 joule per second.
Approach: Use the formula P = W/t, set W=1 and t=1 to frame the sentence.
Define 1 Watt of power.
Power of an agent is 1 Watt if it does work at the rate of 1 Joule per second.
Approach: Base it on P = W/t where W is 1 J and t is 1 s.
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