NCERT Solutions for Class 11 Maths Chapter 10 Exercise 10.2 - Conic Section

NCERT Solutions for Class 11 Maths Chapter 10 Exercise 10.2 - Conic Section

Komal MiglaniUpdated on 06 May 2025, 03:26 PM IST

Have you ever wondered about the shape of the trajectory of a rocket in the air or the arc of a basketball in motion? It is the parabola which is formed when such objects are in motion. The study of parabolas becomes important, as it has wide applications in physics, engineering and astronomy, among others. Also, reflective properties of parabolas are used in solar panels, communication dishes, headlights, etc.

This Story also Contains

  1. NCERT Solutions Class 11 Maths Chapter 10 Exercise 10.2
  2. Topics covered in Chapter 10 Conic Section Exercise 10.2
  3. Class 11 Subject-Wise Solutions


In this exercise, 10.2 of Class 11 Maths Chapter 10 of the NCERT, various aspects of parabolas are discussed. Questions cover a range of topics such as how a parabola is formed, the standard equation of a parabola, its key features, which include focus, vertex, directrix, and latus rectum. The parabola topic is important for a robust understanding of advanced topics such as projectile motion and conic sections in coordinate geometry. If you are looking for NCERT Solutions, you can click on the given link to get NCERT solutions for Classes 6 to 12.

NCERT Solutions Class 11 Maths Chapter 10 Exercise 10.2

Question 1: Find the coordinates of the focus, axis of the parabola, the equation of the directrix and the length of the latus rectum.

$y^2 =12x$

Answer:

Given, a parabola with equation

$y^2 =12x$

This is parabola of the form $y^2=4ax$ which opens towards the right.

So,

By comparing the given parabola equation with the standard equation, we get,

$4a=12$

$a=3$

Hence,

Coordinates of the focus :

$(a,0)=(3,0)$

Axis of the parabola:

It can be seen that the axis of this parabola is X-Axis.

The equation of the directrix

$x=-a,\Rightarrow x=-3\Rightarrow x+3=0$

The length of the latus rectum:

$4a=4(3)=12$.

Question 2: Find the coordinates of the focus, axis of the parabola, the equation of the directrix and the length of the latus rectum.

$x^2 = 6y$

Answer:

Given, a parabola with equation

$x^2 =6y$

This is parabola of the form $x^2=4ay$ which opens upward.

So,

By comparing the given parabola equation with the standard equation, we get,

$4a=6$

$a=\frac{3}{2}$

Hence,

Coordinates of the focus :

$(0,a)=\left (0,\frac{3}{2}\right)$

Axis of the parabola:

It can be seen that the axis of this parabola is Y-Axis.

The equation of the directrix

$y=-a,\Rightarrow y=-\frac{3}{2}\Rightarrow y+\frac{3}{2}=0$

The length of the latus rectum:

$4a=4(\frac{3}{2})=6$.

Question 3: Find the coordinates of the focus, axis of the parabola, the equation of the directrix and the length of the latus rectum.

$y^2 = -8x$

Answer:

Given, a parabola with equation

$y^2 =-8x$

This is parabola of the form $y^2=-4ax$ which opens towards left.

So,

By comparing the given parabola equation with the standard equation, we get,

$-4a=-8$

$a=2$

Hence,

Coordinates of the focus :

$(-a,0)=(-2,0)$

Axis of the parabola:

It can be seen that the axis of this parabola is X-Axis.

The equation of the directrix

$x=a,\Rightarrow x=2\Rightarrow x-2=0$

The length of the latus rectum:

$4a=4(2)=8$.

Question 4: Find the coordinates of the focus, axis of the parabola, the equation of the directrix and the length of the latus rectum.

$x^2 = -16y$

Answer:

Given, a parabola with equation

$x^2 =-16y$

This is parabola of the form $x^2=-4ay$ which opens downwards.

So,

By comparing the given parabola equation with the standard equation, we get,

$-4a=-16$

$a=4$

Hence,

Coordinates of the focus :

$(0,-a)=(0,-4)$

Axis of the parabola:

It can be seen that the axis of this parabola is Y-Axis.

The equation of the directrix

$y=a,\Rightarrow y=4\Rightarrow y-4=0$

The length of the latus rectum:

$4a=4(4)=16$.

Question 5: Find the coordinates of the focus, axis of the parabola, the equation of the directrix and the length of the latus rectum.

$y^2 = 10x$

Answer:

Given, a parabola with equation

$y^2 =10x$

This is parabola of the form $y^2=4ax$ which opens towards the right.

So,

By comparing the given parabola equation with the standard equation, we get,

$4a=10$

$a=\frac{10}{4}=\frac{5}{2}$

Hence,

Coordinates of the focus :

$(a,0)=\left(\frac{5}{2},0\right)$

Axis of the parabola:

It can be seen that the axis of this parabola is X-Axis.

The equation of the directrix

$x=-a,\Rightarrow x=-\frac{5}{2}\Rightarrow x+\frac{5}{2}=0\Rightarrow 2x+5=0$

The length of the latus rectum:

$4a=4(\frac{5}{2})=10$.

Question 6: Find the coordinates of the focus, axis of the parabola, the equation of the directrix and the length of the latus rectum.

$x^2 = -9y$

Answer:

Given, a parabola with equation

$x^2 =-9y$

This is parabola of the form $x^2=-4ay$ which opens downwards.

So

By comparing the given parabola equation with the standard equation, we get,

$-4a=-9$

$a=\frac{9}{4}$

Hence,

Coordinates of the focus :

$(0,-a)=\left (0,-\frac{9}{4}\right)$

Axis of the parabola:

It can be seen that the axis of this parabola is Y-Axis.

The equation of the directrix

$y=a,\Rightarrow y=\frac{9}{4}\Rightarrow y-\frac{9}{4}=0$

The length of the latus rectum:

$4a=4\left(\frac{9}{4}\right)=9$.

Question 7: Find the equation of the parabola that satisfies the given conditions:

Focus (6,0); directrix $x = - 6$

Answer:

Given, in a parabola,

Focus : (6,0) And Directrix : $x = - 6$

Here,

Focus is of the form (a, 0), which means it lies on the X-axis. And Directrix is of the form $x=-a$ which means it lies left to the Y-Axis.

These are the condition when the standard equation of a parabola is.$y^2=4ax$

Hence the Equation of Parabola is

$y^2=4ax$

Here, it can be seen that:

$a=6$

Hence the Equation of the Parabola is:

$\Rightarrow y^2=4ax\Rightarrow y^2=4(6)x$

$\Rightarrow y^2=24x$.

Question 8: Find the equation of the parabola that satisfies the given conditions:

Focus (0,–3); directrix $y = 3$

Answer:

Given,in a parabola,

Focus : Focus (0,–3); directrix $y = 3$

Here,

Focus is of the form (0,-a), which means it lies on the Y-axis. And Directrix is of the form $y=a$ which means it lies above X-Axis.

These are the conditions when the standard equation of a parabola is $x^2=-4ay$.

Hence the Equation of Parabola is

$x^2=-4ay$

Here, it can be seen that:

$a=3$

Hence the Equation of the Parabola is:

$\Rightarrow x^2=-4ay\Rightarrow x^2=-4(3)y$

$\Rightarrow x^2=-12y$.

Question 9: Find the equation of the parabola that satisfies the given conditions:

Vertex (0,0); focus (3,0)

Answer:

Given,

Vertex (0,0) And focus (3,0)

As vertex of the parabola is (0,0) and focus lies in the positive X-axis, The parabola will open towards the right, And the standard equation of such parabola is

$y^2=4ax$

Here it can be seen that $a=3$

So, the equation of a parabola is

$\Rightarrow y^2=4ax\Rightarrow y^2=4(3)x$

$\Rightarrow y^2=12x$.

Question 10: Find the equation of the parabola that satisfies the given conditions:

Vertex (0,0); focus (-2,0)

Answer:

Given,

Vertex (0,0) And focus (-2,0)

As vertex of the parabola is (0,0) and focus lies in the negative X-axis, The parabola will open towards left, And the standard equation of such parabola is

$y^2=-4ax$

Here it can be seen that $a=2$

So, the equation of a parabola is

$\Rightarrow y^2=-4ax\Rightarrow y^2=-4(2)x$

$\Rightarrow y^2=-8x$.

Question 11: Find the equation of the parabola that satisfies the given conditions:

Vertex (0,0) passing through (2,3) and axis is along x-axis.

Answer:

Given

The Vertex of the parabola is (0,0).

The parabola is passing through (2,3) and axis is along the x-axis, it will open towards right. and the standard equation of such parabola is

$y^2=4ax$

Now since it passes through (2,3)

$3^2=4a(2)$

$9=8a$

$a=\frac{8}{9}$

So the Equation of Parabola is ;

$\Rightarrow y^2=4\left(\frac{9}{8}\right)x$

$\Rightarrow y^2=\left(\frac{9}{2}\right)x$

$\Rightarrow 2y^2=9x$

Question 12: Find the equation of the parabola that satisfies the given conditions:

Vertex (0,0), passing through (5,2) and symmetric with respect to y-axis.

Answer:

Given a parabola,

with Vertex (0,0), passing through (5,2) and symmetric with respect to the y-axis.

Since the parabola is symmetric with respect to Y=axis, it's axis will ve Y-axis. and since it passes through the point (5,2), it must go through the first quadrant.

So the standard equation of such parabola is

$x^2=4ay$

Now since this parabola is passing through (5,2)

$5^2=4a(2)$

$25=8a$

$a=\frac{25}{8}$

Hence the equation of the parabola is

$\Rightarrow x^2=4\left ( \frac{25}{8} \right )y$

$\Rightarrow x^2=\left ( \frac{25}{2} \right )y$

$\Rightarrow 2x^2=25y$


Also read,


Topics covered in Chapter 10 Conic Section Exercise 10.2

1. Standard Equations of Parabolas
This section explores the general and standard equations of a parabola, which help in identifying the orientation and key features of the parabola.

2. Focus and Directrix of Parabolas
In this topic, we learn about how every point on a parabola maintains an equal distance from a fixed point (focus) and a fixed line (directrix), which defines the shape of a parabola.

3. Axis of Symmetry
The axis of symmetry in a parabola is a line that divides the parabola into two mirror-image halves, and the axis of symmetry passes through the vertex and focus.

4. Latus Rectum
Latus rectum is known as a line segment perpendicular to the axis of symmetry that also passes through the focus.

5. Applications

Various applications of parabolas are widely used in designing satellite dishes, car headlights, bridges, and in solving physics problems involving projectile motion.

Also Read

Class 11 Subject-Wise Solutions

Follow the links to get your hands on subject-wise NCERT textbooks and exemplar solutions to ace your exam preparation.

NCERT Solutions of Class 11 Subject Wise

Subject Wise NCERT Exampler Solutions


Frequently Asked Questions (FAQs)

Q: Find the coordinates of the focus of the parabola $y^2$ = 8x .
A:

Equation of the parabola => $y^2$ = 8x 

Comparing  with  the given  equation  => $y^2$ = 4ax

a = 2

The coordinate of the focus of the parabola is (2, 0)

Q: Find the coordinates of the equation of the directrix of the parabola $y^2$ = 8x .
A:

Equation of the parabola => $y^2$ = 8x 

Comparing  with  the given  equation  => $y^2$ = 4ax

a = 2

The equation of the directrix of the parabola is x = – 2

Q: Find the length of the latus rectum of the parabola $y^2$ = 8x .
A:

Equation of the parabola => $y^2$ = 8x 

Comparing  with  the given  equation  => $y^2$ = 4ax

a = 2

Length of the latus rectum is (4a) = 4 x 2 = 8.

Q: Write the equation of the with focus at (a, 0) directrix x = – a (a > 0)
A:

The equation of the parabola with focus at (a, 0) and directrix x = – a is $y^2$  =  4ax.

Q: What is the length of lotus rectum of the parabola$ y^2$ = 4ax.
A:

The length of the latus rectum of the parabola $y^2$ = 4ax is 4a.

Q: When a ball is throwing in air in influence of gravity, the ball will follow the path ?
A:

When a ball is throwing in the air in presence of gravity, the ball will follow the parabolic path.

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