Question

A thermometer contains 3.00 g of mercury. After it gains 8.4 J of energy  the mercury has reached the 5.00°C mark. What was the initial  temperature of the mercury?

Answer 1

Solution.

$m=3.00g;$

$Q=8.4J;$

$t=5.00^o;$

$c=130J/kg^oC;$

$Q=cm(t-t_0);$

$cmt_0=cmt-Q\implies t_0=\dfrac{cmt-Q}{cm};$

$t_0=\dfrac{130J/kg^oC\sdot3.00\sdot10^{-3}kg\sdot5.00^oC-8.4J}{130J/kg^oC\sdot3.00\sdot10^{-3}kg}=-16.5^oC;$

Answer: $t_0=-16.5^oC.$