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A stone is dropped into a pond. Waves in the form of circles are generated and radius of outermost ripple increases at the rate of 5 cm/sec. then area increased after 2 sec is . . .A. `100 pi cm^(2)//sec`B. `40 cm^(2)//sec`C. `50 cm^(2)//sec`D. `25 cm^(2)//sec` |
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Answer» Correct Answer - A We have, `(dr)/(dt)=5 cm//sec` `A=pir^(2)rArr(dA)/(dt)=2pir(dr)/(dt)` `rArr(dA)/(dt)=2pi(10)/(5)=100 picm^(2)//sec` |
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