Question

Question 1: Figure below is symmetrical about the vertical Y axis. Calculate the distance of the centre of area (centroid) of cross section from the base. 1 m 0.2 m 0.6 m 0.2 m X 0.2 m 0.8 m

Answer 1

We want here centroid from base .

Use formula of centroid

Shape : I section

Divide the I section into three parts .

Find y1 , y2 and y3 from base . And find area of elements

TY Im D ہ 0.2m I section is symmetrical y 0.6 m 0,015 K 72 Y = 0.3133m buse. will o 3 0.2m 20 a bored Y-axis. so that The centroid lies on the y-axis. folmuilas ý = { Yi Ai { Ai &o.2m- k~0.8m Y, -0.2 +0.6 +0.2 -0.9m 2. Y2 = 0.2 + 0.6 -0.5m 2 A,Y, + AzY2+ A₂ Yg Ait A2+ Az Y₂ = 0.2 - 0.1 2 Air IX 0.2 0.2 m m2 - (0.20.9) + (0.5X1.27+(0,1* 1.6) 2 0.2 +1.2 + 1.6 Az - 0.6 X0.2 - 1.2m Az = 0.280.8=1.6m² 0.18 + 0.6 + 0.16 = 3 0.94 3 17 20.3133 m Ý = 31.33 cm Y = 313. 33 mm