An arch is in the form of a parabola with its axis vertical. The arch is 10 m high and 5 m wide at the base. How wide is it 2 m from the vertex of the parabola?
An arch is in the form of a parabola with its axis vertical. The arch is 10 m high and 5 m wide at the base. How wide is it 2 m from the vertex of the parabola?

We realize that the beginning of the facilitate plane is taken at the vertex of the curve, where its upward pivot is along the positivey-axis.

Diagrammatic portrayal is as per the following:

NCERT Solutions for Class 11 Maths Chapter 11 – Conic Sections image - 2

The condition of the parabola is of the structure

    \[{{x}^{2}}~=\text{ }4ay~\]

(as it is opening upwards).

It is given that at base curve is

    \[10m\text{ }high\text{ }and\text{ }5m\text{ }wide.\]

In this way,

    \[y\text{ }=\text{ }10\text{ }and\text{ }x\text{ }=\text{ }5/2\]

from the above figure.

Unmistakably the parabola goes through point

    \[\left( 5/2,\text{ }10 \right)\]

    \[<span class="ql-right-eqno"> (1) </span><span class="ql-left-eqno">   </span><img src="https://www.learnatnoon.com/s/wp-content/ql-cache/quicklatex.com-593ad01ad2c50f3aee20d7004bb35e9f_l3.png" height="167" width="258" class="ql-img-displayed-equation quicklatex-auto-format" alt="\begin{align*} & \begin{array}{*{35}{l}} So,\text{ }{{x}^{2}}~=\text{ }4ay  \\ {{\left( 5/2 \right)}^{2}}~=\text{ }4a\left( 10 \right)  \\ \end{array} \\ & \begin{array}{*{35}{l}} 4a\text{ }=\text{ }25/\left( 4\times 10 \right)  \\ a=\text{ }5/32  \\ \end{array} \\ \end{align*}" title="Rendered by QuickLaTeX.com"/>\]

we realize the curve is as a parabola whose condition is

    \[~{{x}^{2}}~=\text{ }5/8y\]

We need to discover width, when stature

    \[=\text{ }2m.\]

To discover

    \[x,\text{ }when\text{ }y\text{ }=\text{ }2.\]

At the point when,

    \[y\text{ }=\text{ }2,\]

    \[<span class="ql-right-eqno"> (2) </span><span class="ql-left-eqno">   </span><img src="https://www.learnatnoon.com/s/wp-content/ql-cache/quicklatex.com-4610f3449fd3eeee50e6963d4c3c47ae_l3.png" height="284" width="304" class="ql-img-displayed-equation quicklatex-auto-format" alt="\begin{align*} & {{x}^{2}}~=\text{ }5/8\text{ }\left( 2 \right) \\ & \begin{array}{*{35}{l}} =\text{ }5/4  \\ x\text{ }=\text{ }\surd \left( 5/4 \right)  \\ =\text{ }\surd 5/2  \\ AB\text{ }=\text{ }2\text{ }\times \text{ }\surd 5/2m  \\ =\text{ }\surd 5m  \\ =\text{ }2.23m\text{ }\left( approx. \right)  \\ \end{array} \\ \end{align*}" title="Rendered by QuickLaTeX.com"/>\]

Subsequently, when the curve is

    \[2m\]

from the vertex of the parabola, its width is roughly

    \[2.23m.\]