You are doing an experiment to determine how many passengers would fit into a full-sized plane. If a scale model plane has space
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No force contributes to density, the density is a physical quantity that is defined as being 
the raport between the mass of the object and its volume. However if you want to measure the density of an object you might want to determine its gravity force (weight) 
from which knowing the gravitational acceleratin you can find its mass 
where
is given in Newtons and 
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