Question

What do u mean by density ??
Is density more in wood or in iron

Answer 1

density is the mass per unit volume .
density of iron is more

Answer 2

The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used fordensity is ρ (the lower case Greek letter rho), although the Latin letter D can also be used. ... Thus a relativedensity less than one means that the substance floats in water.

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How do you find the density of an object?

To find the density of any object, you need to know the Mass (grams) of the object, and its Volume (measured in mL or cm³). Divide the mass by the volume in order to get an object's Density.

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It depends on how you measure the tonne.  You see, the apparent weight on the scales is the true weight less the weight of the displaced air.  

A ton of iron displaces less air than a ton of wood.  So the apparent weights of an equal true weights of iron and wood, iron is heavier.  But to get a ton apparent, you need more wood because wood displaces more air.

Wood floats in water, iron sinks.  The apparent density of wood in water is negative, for iron it's positive.