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CBSE Class 9 Answered

a body standing near the edge of a cliff 125m above a river throws a stone downwards with a speed of 10m/s. Find -
(i) with what speed will the stone hit water and,
(ii) how long will it take to descend 
Asked by rahulsarawgee04 | 16 Jun, 2015, 11:39: AM
answered-by-expert Expert Answer
begin mathsize 12px style Given colon straight s equals 125 space straight m straight u equals 10 space straight m divided by straight s straight g equals 10 space straight m divided by straight s squared left parenthesis straight i right parenthesis When space stone space throws space in space downwards space direction space it space his space the space water space with space speed space straight v using space equation space of space motion comma straight v squared equals straight u squared plus 2 gs straight v squared equals left parenthesis 10 right parenthesis squared plus 2 cross times 10 cross times 125 straight v equals 51 space straight m divided by straight s Stone space will space hit space the space water space with space speed space 51 space straight m divided by straight s left parenthesis ii right parenthesis space To space calculate space time space of space descend comma space straight t using space equation space of space motion comma straight v equals straight u plus gt 51 equals 10 plus 10 cross times straight t 41 equals 10 straight t straight t equals 41 over 10 equals 4.1 space straight s It space will space take space 4.1 space straight s space to space descend end style
Answered by Priyanka Kumbhar | 16 Jun, 2015, 05:12: PM

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