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# NCERT Books for Class 9 Science Chapter 8

Last updated date: 04th Aug 2024
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Free NCERT Books download for Class 9 Science Chapter 8 - Motion on Vedantu. Students can also download the NCERT Solutions for Class 9 Science Chapter 8 Motion - Free PDF. Register Online for Class 9 Science tuition on Vedantu to score more marks in your examination. Vedantu is a platform that provides free CBSE Solutions (NCERT) and other study materials for students. Math Students who are looking for the better solutions, they can download Class 9 Math NCERT Solutions to help you to revise the complete syllabus and score more marks in your examinations.

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## Benefit Of Class 9 Science- Motion

NCERT Class 9 Science chapter 8 deals with Motion and how the motion affects the movement of an object. The chapter also explains concepts like velocity, speed, types of motions and the relationship between the position of the object with velocity and time. Also, there are several diagrams, graphs and examples given to substantiate the theories as well for a better understanding of the topics.

Basically, motion refers to the change in position of an object with change in time. The object could either be at rest or in motion, depending on quantities like distance traveled, velocity, speed, etc. The motion of the object is often described by a reference point or the origin. The next topic in discussion is the motion of an object in a straight line which is the simplest motion. Motion could be either:

• Uniform Motion- Here, an object must cover an equal distance in equal amount of time. For example, the motion of a car moving with same speed

• Non-Uniform Motion- Here, the object travels unequal distances in equal time intervals. For example, a car moving in a crowded area.

One can easily calculate the speed of the object by dividing the distance traveled by the object in unit time. The S.I. unit of speed is m/s or km/hr. Most of the time, the objects travel at non-uniform speed so:

$\text{Average speed} = \frac{\text{Total distance}}{\text{Total time}}$

Similarly , velocity of an object is the displacement traveled by it in a given time. Velocity is constant in case of uniform motion in a straight line but changes with respect to time in non uniform motion.

Acceleration involves rate of change in velocity in unit time and is calculated by:

$Acceleration (a)= \frac{\text{change in velocity}}{\text{time taken}}$

To calculate the average velocity in a motion having constant acceleration, the formula is:

$\text{Average Velocity}= \frac{(\text{Initial Velocity + Final Velocity})}{2} = \frac{(u+v)}{2}$

## FAQs on NCERT Books for Class 9 Science Chapter 8

1. Are graphs important in NCERT Books for Class 9 Science Chapter 8 - Motion?

Using a graph is convenient as it shows the relation between distance or velocity on one hand and time on the other. There are two graphs included in NCERT class 9 chapter 8 Motion.

• Distance-Time Graph:  This graph represents the change in position of the object where the object moves in uniform motion, non-uniform motion, at rest, etc. The distance is marked in the y axis and time in the x axis.

• Velocity- Time Graph: The variation in velocity with respect to time is represented by this graph. The y axis is marked as velocity and x axis as time.

2. What are the three cases of equation of motion by Graphical method in Motion mentioned in NCERT Books for Class 9 Science Chapter 8 - Motion?

When an object moves in uniform motion in a straight line, the equations of motion can be related to the velocity, distance covered in a certain time interval and with a certain acceleration. For this, there are three cases given:

• Velocity-Time relation: Change in acceleration of an object in this graph is given as $\left [ a=\frac{\text{change in velocity}}{\text{Time taken}}\right ]$Based on that, the equation formed is v= u+at where v is the final velocity and u is the initial velocity.

• Position- Time relation: If we consider that an object has moved a certain distance s in time t and at an acceleration a, then the equation formed is $s=ut+\frac{1}{2}at^{2}$ .

• Position- Velocity relation: Same as the above case, the equation formed here is 2as= v2-u2.

3. How do we solve numericals in NCERT Books for Class 9 Science Chapter 8 - Motion?

In between the NCERT class 9 chapter 8 Motion, each section has been clearly segmented along with several activities and exercises with numericals given so that students can solve and practice after each topic. This helps in quicker memorisation of the concept and also helps the student to mark his/her strengths and weaknesses. Numericals are also given at the end of the chapter which tests the complete understanding of the topics in question. For more such numericals, students can follow Vedantu and download study materials for free.

4. How do we learn the concepts in NCERT Books for Class 9 Science Chapter 8 - Motion?

Concepts in Physics cannot be memorized at one go. It has to be understood first as it contains formulas and several theories related to them. After completing the chapter, students must read the summary of the chapter so that they can recollect the crux of the sections and clear doubts, if any. Furthermore, they can make short notes or follow video tutorials to clarify different concepts as well.  Vedantu helps students in building a strong foundation through their study resources available for free on their website.

5. What kind of questions are asked in the exam from NCERT Books for Class 9 Science Chapter 8 - Motion?

Most of the questions asked in the class 9 Physics paper include short answer type questions or Multiple Choice Questions (MCQs) and numericals. The numericals are easy and students can score full marks if the formulas are revised properly.  For short answer types, students must be thorough with the chapter because there are certain technical terms in Physics which students, sometimes, forget ahead of the exam. Hence students must pay close attention to the smallest details in the chapter which can be tedious initially, but will get easier once the short notes are revised.