Find the ratio of the weights, as measured by a spring balance, of a 1 kg block of iron and a 1 kg block of wood. Density of iron = 7800 kg m-3, density of wood = 800 kg m-3 and density of air = 1293 kg m-3.

Given, Density of iron, ,

density of wood,


density of air


The objects can be thought of as fully immersed in air. Therefore, there will be a buoyant force working upwards.


Let mass of iron be and that of wood be . Let there volumes be and respectively.


The weight of iron block becomes, —————(1)


Similarly, weight of wooden block is —————(2)


Taking ratio of (1) and (2)



(ANS)


1