 # NCERT Solutions for Class 9 Science Chapter 8

## NCERT Solutions for Class 9 Science Chapter 8 - Motion

Q1: Explain the distance-time graph and velocity-time graph.

A1: Distance-Time Graph

• Distance-Time graphs show the change in position of an object with respect to time.

• Linear variation = uniform motion & non-linear variations imply non- uniform motion.

• The slope gives us speed.

Velocity-Time Graph

• Velocity-Time graphs show the change in velocity with respect to time.

• Slope gives acceleration.

• The area under the curve gives the displacement.

• Line parallel to the x-axis implies constant velocity.

Q2: What are the topics and exercises covered in the NCERT Solutions for class 9 science chapter 8 by Vedantu?

A2: The following are the topics covered in the NCERT Solutions for class 9 science chapter 8 by Vedantu.

• Ex 8.1 - Describing Motion

• Ex 8.1.1 - Motion Along a Straight Line

• Ex 8.1.2 - Uniform Motion and Nonuniform Motion

• Ex 8.2 - Measuring the Rate of Motion

• Ex 8.2.1 - Speed With Direction

• Ex 8.3 - Rate of Change of Velocity

• Ex 8.4 - Graphical Representation of Motion

• Ex 8.4.1 - Distance–Time Graphs

• Ex 8.4.2 - Velocity-Time Graphs

• Ex 8.5 - Equations of Motion by Graphical Method

• Ex 8.5.1 - Equation For Velocity-Time Relation

• Ex 8.5.2 - Equation For Position-Time Relation

• Ex 8.5.3 - Equation For Position–Velocity Relation

• Ex 8.6 - Uniform Circular Motion.

The above chapters are tested through several exercises. The exercises for which solutions are available in NCERT Solutions for class 9 science chapter 8 are:

• Exercise 8.1 - 3 Questions with Solutions.

• Exercise 8.2 - 5 Questions with Solutions.

• Exercise 8.3 - 3 Questions with Solutions.

• Exercise 8.4 - 4 Questions with Solutions.

• Exercise 8.5 - 5 Questions with Solutions.

• Exercise 8.6 - 10 Questions with Solutions.

Q3: What is the difference between speed and velocity?

A3: The major difference between speed and velocity are mentioned below:

• Velocity - refers to the displacement of a given object over a time interval. The velocity has a specific direction. Velocity can hold a negative value as well. The formula for velocity is given by - Velocity = displacement/time.

• Speed - Refers to the distance moved or travelled by an object over a time interval. Speed does not have any direction. Most importantly, speed cannot hold a negative value. The formula for speed is given by - Speed = distance/time.

Q4: Give a few examples of action and Newtons’ third law of motion.

A4: Newton’s third law states that every action has an equal and opposite reaction. Some example is as mentioned below:

• Swimming - A swimmer while swimming pushes the water backwards by their hands. In return the water pushes the swimmer forwards, thus allowing him to go forward during swimming.

• Walking - During walking, a person will push the ground in a backward direction. The ground in return pushes the person in the forward direction, thereby making him/her walk.

• Flying - A bird in the process of flying pushes the air downwards with the aid of its wings. In return, the air pushes the bird upwards.

• Sleeping - While a person is sleeping on a bed, his weight is opposed by a reaction force from the bed. This results in both the forces cancel each other out, and the person enjoys the equilibrium position.

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