[tex]\qquad\qquad\huge\underline{{\sf Answer}}♨[/tex]
Heat capacity of body 1 :
[tex]\qquad \sf \dashrightarrow \:m_1s_1[/tex]
Heat capacity of body 2 :
[tex]\qquad \sf \dashrightarrow \:m_2s_2[/tex]
it's given that, the the head capacities of both the objects are equal. I.e
[tex]\qquad \sf \dashrightarrow \:m_1s_1 = m_2s_2[/tex]
[tex]\qquad \sf \dashrightarrow \:m_1 = \dfrac{m_2s_2}{s_1} [/tex]
Now, consider specific heat of composite body be s'
According to given relation :
[tex]\qquad \sf \dashrightarrow \:(m_1 + m_2) s' = m_1s_1 + m_2s_2[/tex]
[tex]\qquad \sf \dashrightarrow \:s' = \dfrac{ m_1s_1 + m_2s_2}{m_1 + m_2}[/tex]
[tex]\qquad \sf \dashrightarrow \:s' = \dfrac{ m_2s_2+ m_2s_2}{ \frac{m_2s_2}{s_1} + m_2 }[/tex]
[ since, [tex] m_2s_2 = m_1s_1 [/tex] ]
[tex]\qquad \sf \dashrightarrow \:s' = \dfrac{ 2m_2s_2}{ m_2(\frac{s_2}{s_1} + 1)}[/tex]
[tex]\qquad \sf \dashrightarrow \:s' = \dfrac{ 2 \cancel{m_2}s_2}{ \cancel{m_2}(\frac{s_2}{s_1} + 1)}[/tex]
[tex]\qquad \sf \dashrightarrow \:s' = \dfrac{ 2 s_2}{ (\frac{s_2 + s_1}{s_1} )}[/tex]
[tex]\qquad \sf \dashrightarrow \: s' = \dfrac{2s_1s_2}{s_1 + s_2} [/tex]
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