Question

The elastic limit of brass is $379\, MPa$. What should be the minimum diameter of a brass rod if it is to support a $400 \,N$ load without exceeding its elastic limit ?

• A. $1.16\, mm$
• B. $0.90\, mm$
• C. $1.36\, mm$
• D. $1.00\, mm$

Answer 1

Answer: (A)

$\frac{F}{A} =\text{stress} $
$ \frac{400 \times4}{\pi d^{2}} = 379 \times10^{6} $
$ d^{2} = \frac{1600}{\pi \times379 \times10^{6}} = 1.34 \times10^{-6} $
$ d = \sqrt{1.34 } \times10^{-3} = 1.15 \times10^{-3} m $