Question: what is the relation between calorie and mechanical equivalent of heat?
Answer: Where W is the work done calculated in Joules and Q is the heat change calculated in calories. J normally has a unit of J/cal. But in SI units calorie is converted to Joule, changing the magnitude too for J. Hence in SI system J becomes 1/4.18 times its previous value with dimensions Joule/Joule(no units hence).