Question

The mass of a solid iron cube of side 4 cm is to be determined. Of the 4 spring balances available, the one best suited for this purpose would be having :

a) Range = 0-100 g, L.C = 1 g

b) Range = 0-100 g, L.C = 5 g

c) Range = 0-1000 g, L.C = 10 g

d) Range = 0-1000 g, L.C = 25 g

Explain with complete justifications.

Answer 1

Given:
side of solid iron cube=s= 4cm
density of iron= d= 7.8g/ cm3
volume of cube = s*s*s
=4×4×4
=64cm3
As we know,
density= mass/ volume
mass= density x volume
=7.8 *64
=499.2 gm
As the mass is 499.2 gm , the spring balance range should be 0-1000g
Least count is the smallest measurement we can measure.
As mass to be measured is in decimal value.Its better to select the least count as 10g
Hence option C is correct answer.
Spring balance with 0-1000g and least count 10g

Answer 2

of the iron cube :-
length of each side = 4 cm
volume = (4)^3 cm^3 = 64 cm^3

we know
density of iron = 7.8 g/ cm^3

mass = density x volume
=( 7.8 x 64 ) g
= 499.2 g

we observe:-
mass of cube is more than 100g

therefore the range of spring of 1-1000g is suitable for measuring the mass of the cube
____________________________

correct option:-

c) range = 1-1000 g , L C = 10g