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# NCERT Books for Class 9 Science Chapter 9

Last updated date: 05th Aug 2024
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## NCERT Books for Class 9 Science - Force and Laws of Motion - Free PDF Download

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NCERT Books for Class 9 Science Chapter 9
Force And Laws of Motion in One Shot (Complete Chapter) CBSE Class 9 Science Chapter 9 [Term 1 Exam]
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## Brief Idea About The Chapter

NCERT Books for Class 9 Chapter 9 discusses the Forces and Laws of Motion which have been discussed only briefly in the previous chapter (Chapter 8- Motion). In this chapter, we will study how forces like pushing, pulling or hitting an object can change the velocity of an object or change the direction of motion and even the shape and size of the object. It also discusses the different laws of motion which is the most important section of this chapter.

In order to move or stop a stationary object, some force is applied which in turn changes the velocity, speed, acceleration, direction, shape and size of the object. The concept of pushing, pulling or hitting an object is the force.

There are two kinds of forces which determine the motion of an object: Balanced and Unbalanced forces.

The Balanced Force is applied when an object, from either end, is pulled or pushed with equal force such that the motion of the object becomes zero, i.e., the object does not move. Under Unbalanced Force, the side with greater force will dominate and will cause movement in the direction of the weaker force. For example, when riding a bike, if balanced force is applied on all points of the object and no external force is applied, the object will move with a uniform velocity. But if unbalanced force is applied along with an external force on one end, the direction or speed of the object will change. Hence, to accelerate the motion of the bike, unbalanced force is needed. But even though the force is stopped, the object will continue to move with the velocity it has gained up till a certain point.

The other topics which have been discussed under NCERT Books for Class 9 chapter 9 Forces and Laws of Motion along with examples and numericals are as follows:

• 9.2- First Law of Motion

• 9.3- Inertia and Mass

• 9.4- Second Law of Motion

• 9.4.1- Mathematical Formulation of Second Law of Motion

• 9.5- Third Law of Motion

• 9.6- Conservation of Momentum

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

1. What are the three Laws of motion mentioned in NCERT Books for Class 9 chapter 9 Forces and Laws of Motion?

The three Laws of motion discussed in this chapter are the most important sections and are often asked in the exams. They are the following:

• First Law of Motion: An object continues to be in the state of rest or of uniform motion along the straight line unless acted upon by an unbalanced external force.

• Second Law of Motion: The rate of change of momentum of an object is proportional to the applied unbalanced force and the change takes place  in the direction of the force.

• Third Law of Motion: To every action, there is an equal and opposite reaction.

2. How do we derive the mathematical formulation of the Second Law of Motion?

The Second Law of Motion states that the rate of change of momentum of an object is proportional to the applied unbalanced force in the direction of the force. Suppose an object of mass m is moving in a straight line with an initial velocity u and is uniformly accelerated at a velocity v in time t with a constant force F. We know that acceleration a= (v-u)/t. Hence the formula for this motion is F=ma. The S.I of force is kg m/s2 or N.

3. Is the NCERT Class 9 chapter 9 Forces and Laws of Motion difficult?

NCERT Class 9 chapter 9 Forces and Laws of Motion is not a very difficult chapter but is tricky to understand depending on the questions asked. Students must be very clear with the concepts involving the laws since most of the questions, be it short answer types or Multiple Choice Questions or numericals, will be worded in a manner such that students might get confused. Hence, this chapter has to be revised, practiced and prioritized to score well in the exam.

4. Can we download the NCERT Class 9 chapter 9 Forces and Laws of Motion online?

NCERT Books Free Download for Class 9 Science Chapter 9 - Force and Laws of Motion are available online on Vedantu. Vedantu has been helping students bring out their best abilities and capabilities by preparing new sample papers and updating them with time. Study materials have also been uploaded for students to download at any time which can be used for revision ahead of the test. Students need not search online for too many resources since they can find  all of it in one!

5. Are there numericals given in NCERT Class 9 chapter 9 Forces and Laws of Motion?

Yes, numericals are mainly based on the three Laws of Motion, especially in the case of the Second Law of Motion. These numericals only test the basic knowledge and understanding of the concepts of the students and are given in the form of exercises both in between as well as after the chapters. The numericals are not tough but tricky so that students can adapt themselves to the different levels of difficulty which will boost their performance in the exams and also prepare them for the worst.