Question

Question 12
For a square beam of size 300 mm x 300
mm if the maximum allowable bending
stress is 100 MPa, calculate the maximum
bending moment it can carry safely.
100 KN m
250 KN m
300 KN m
450 KN m

Answer 1

Answer:250

Explanation:

Answer 2

Answer:

100KNm can be carried out safely.

Explanation:

From the question we have,

The area of square=300mm×300mm=900×10⁻⁶m²

The bending stress=100 MPa=100×10⁶Pa

The stress is calculated as,

$\mathrm{S=\frac{F}{A} }$                (1)

Where,

S=stress

F=force acting

A= area over which the force is acting

Inserting the values of "S" and "A" in equation (1) we get;

$\mathrm{100\times 10^6=\frac{F}{900\times 10^{-6}} }$

$\mathrm{F=100\times 10^6\times 900\times 10^{-6}}$

$\mathrm{F=100\times 900}$

$\mathrm{F=9\times 10^4\ N}$       (2)

The bending moment is calculated as,

$\mathrm{\tau=F\times l}$          (3)

Where,

τ=bending moment of the square

F=the force which acts over the area of the square

l=length of the square=4×Side of the square

Inserting the values of "F" and "l" in equation (3) we get;

$\mathrm{\tau=9\times 10^4\times 4\times 300\times 10^{-3}}$

$\mathrm{\tau=108\times 10^3\ Nm}$

$\mathrm{\tau=108\ KNm}$

$\mathrm{\tau=108\ KNm\approx 100KNm}$

So, 100KNm can be carried out safely.

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