Question

A massless beam has a loading pattern as shown in the figure. The beam is of rectangular cross- section with a width of 30mm and height of 100 mm.
The maximum bending moment occurs at

• A. location B
• B. 2675 mm to the right of A
• C. 2500 mm to the right of A
• D. 3225 mm to the right of A

Answer 1

The correct option is C 2500 mm to the right of A



$R_A+R_B=6000N$
Taking moment about A
$600\times 3-R_C\times 4=0$
$\Rightarrow$ $R_c=4500N$
$R_A=1500N$
Taking any section $xm$ from A.
Shear force $=1500-300(x-2)$
and maximum bending moment occurs where shear force = 0
$\Rightarrow$ $1500-3000(x-2)=0$
$x=2.5m$
or $2500mm$ from A