Why is the work output of any real machine less than the work needed to operate it

It is necessary to determine the specific heat of an unknown object. the mass of the object is 201.0g it is determined experimentally that it takes 15j to raise the temperature 10°c. what is the specific heat of the object? 3,020,000 j/kg ∙ k 1500 j/kg ∙ k 0.00130 j/kg ∙ k 7.46 j/kg ∙ k