NCERT Solutions Class 9 Science - Chapter 7 Motion - PDF Download

7.1 Describing Motion: The process of motion is the alteration of an object's or a group of objects' position relative to its environment over a specified time period. Motion is a fundamental principle of physics and aids in the comprehension of the movement and interaction of objects in the physical environment. The describing motion includes variables such as displacement, velocity, speed, and acceleration.

Subtopics covered in the section 7.1 Describing Motion:

      7.1.1 motion along a straight line

      7.1.2 uniform motion and non-uniform motion

7.2 Measuring the Rate of Motion: Different quantities and units can be used to measure the rate of motion, depending on the particular aspect of motion that is being measured.

Subtopics covered in the section 7.2 Measuring the Rate of Motion:

      7.2.1 speed with direction

7.3 Rate of change of velocity: The rate at which the velocity of an object changes over time is referred to as acceleration. This can be due to changes in velocity, changes in direction, or a combination of both.

7.4 Graphical Representation of Motion: Graphs are an effective tool for visualizing various aspects of motion. This article outlines some of the most commonly used graphical representations of motion, as well as the quantities they illustrate.

Subtopics covered in the section 7.4 Graphical Representation of Motion:

      7.4.1 Distance-time Graphs

      7.4.2 velocity-time graphs

7.5 Equations of Motion: When an object is moving in a straight line with a uniform velocity, you can measure its speed, acceleration, and distance over a given time interval using a series of equations called the equations of motion.

7.6 Uniform Circular Motion: The term uniform circular motion is used to describe the movement of an object in a circular motion at a constant velocity. In this form of motion, the velocity remains constant, but the direction of the object is constantly changing, resulting in acceleration. The acceleration of the object is directed toward the center of its circular path, and is referred to as Centripetal Acceleration.

Key Features of Class 9 Science Chapter 7

Class 9 Science Chapter 7, "Motion," provides an introduction to the fundamental concepts of motion, including its importance in everyday life, the various types of motion seen in the environment, and the measurement of motion and associated mathematical formulas. 

• This chapter also explains the concept of distance, which is the total length of a path taken by an object, and displacement, which is the movement of an object from one direction to another. 

• Speed and velocity are also discussed, with speed being the distance traveled per unit time and velocity being the displacement of an object per unit time (including direction). Finally, a comparison of speed and velocity is provided.

• Acceleration is the speed at which something changes. We'll look at how to calculate it and its units, plus and minus accelerations. We'll also look at the equations of motion used to figure out uniformly accelerated motion, and how to use them to solve motion-related problems.

• Finally, we'll look at the graph of motion, from position-time to velocity-time to acceleration-time, and how to interpret the slopes and areas underneath the curves. We'll also break down uniform motion into two types, based on how fast it moves.

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Frequently Asked Questions

Question 1: What is Motion?

Answer 1: Motion is the alteration of an object's position relative to its environment. It is the movement of an object relative to its environment over a specified period of time.

Question 2:  How is distance different from displacement?

Answer 2: Distance is the total distance an object travels, while displacement is how far an object moves from its starting point to its ending point, regardless of where it started.