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The length of a rubber cord is l_1 metres when the tension in it is 4N and l_2metres when the tension is 5N. Then the length in meters when the tension is 9 N is |
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Answer» Solution :Let L be the original length and `l_3`be the length of the wire when the TENSION is 9N. ` rArr (l_1 - l) prop 4......(1), (l_2-l) prop 5........(2)` `(l_3 - l) prop 9...........(3)` From (1) and (2) `(l_1- l)/(l_2 - l) = 4/5 rArr 5l_1- 5l= 4l_2 - 4l` `l = 5l_1 - 4l_2`...(4) From (1) and (3) `(l_1 - l)/(l_3 - l) = 4/9 rArr (l_1 - (5l_2 - 4l_2))/(l_3 - (5l_1 - 4l_2)) = 4/9` `rArr (l_2 - 5l_1 + 4l_2)/(l_3 - 5l_1 + 4l_2) = 4/9 rArr (4l_2 - 4l_1)/(l_3 - 5l_1 + 4l_2) = 4/9` ` rArr 36l_2 - 36l_1 = 4l_3 = 20l_2 + 16l_2` ` 20l_2 - 16l_1= 4l_3 ` `l_3 = 5l_2 - 4l_1` |
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