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)