Q. 53.6( 5 Votes )

# A beam is supported at its ends by supports which are 12 m apart. Since the load is concentrated at its center, there is a deflection of 3 cm at the center, and the deflected beam is in the shape of a parabola. How far from the center is the deflection 1 cm?

Answer :

Given: A beam is supported at its ends by supports which are 12 m apart. There is a deflection of 3 cm at the center, and the deflected beam is in the shape of a parabola.

Need to find: How far from the center is the deflection 1 cm

Here EF are the ends of the beam and they are 12 m apart.

IJ is the deflection of 3 cm at the center.

We know, that the distance IF = m = 600 cm and the deflection IJ = FH = 3 cm.

So, the coordinate of the point F is (600, 3)

Let, the equation of the parabola is: x^{2} = 4ay

F point is on the parabola. So, putting the coordinates of F in the equation we get,

x^{2} = 4ay

⇒ 3600 = 4a x 3

⇒ a = 300

Here KL denotes the deflection of 1 cm.

So, at the point L the value of y-coordinate is (3 – 1) = 2

So, by the equation,

⇒ x^{2} = 4ay = 4 x 300 x 2 = 2400

⇒ x = 49 cm.

So, the distance of the point of 1 cm deflection from the center is 49 cm.

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RS Aggarwal - Mathematics