Answer:
[tex] \boxed{(i).... 40cm}\\ \boxed{(ii).... 18cm}\\ \boxed{(iii).... 7.5N
}\\ [/tex]
Explanation:
[tex](i).... \\ the \: weight \: of \: the \: rod \: acts \: at \: the \: center \\ which \: is \: the \: half \: of \: 80cm = 40cm \\ (ii).... \\ let \: the \: distance \: be \: \boxed{d}...then \: 22 + d = 40 \\ d = 40 - 22 = 18cm \\ (iii).... \\let \: the \: weight \: of \: the \: metal \: rod \: be \: \boxed{ w} \\ taking \: the \: moment \: about \: the \: string \to \\ 15 \times (22 - 13) = 18w \\ 18w = (9)(15) \\ 2w = 15 \\ w = 7.5N[/tex]
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