Question

One cubic meter of mild steel weighs about

• A. $1000kg$
• B. $3625kg$
• C. $7850kg$
• D. $12560kg$

Answer 1

The correct option is C $7850kg$

Density of mild steel is given as $\rho =7850\frac{kg}{m^3}$
So, in $1m^3$ of mild steel weight $W=\rho \times V$
$W=7850kg$
Note : Formulae for unit weight of steel bar
$=\frac{D^2}{162.28}\frac{kg}{m}$
Where, $D=\text{Diameter of bar in (mm)}$
$\Rightarrow$ Above formulae is useful to find out the weight of steel bars if length of the steel bar is known.
$\Rightarrow$ Length of $1$ steel bar is usually $12m$
$\Rightarrow$ At site, steel bar is ordered in ''Weight unit'' (i.e. tonnes), that is why above formulae is very useful.
Derivation of above formulae:
Weight of steel bar per meter $=\text{Area of steel}\times \text{Density of steel}$
$=(\frac{\pi }{4}\times D^2)m^2\times 7850\frac{kg}{m^3}\times 1m$
$=\frac{3.14}{4}\times D^2\times 7850$
$=\frac{D^2\times \left(6162.25\right)}{1000\times 1000}$
$=D^2\times 0.006162$
$=\frac{D^2}{162.28}\frac{kg}{m}$