NCERT Solutions for Class 9 Science Chapter 4 Describing Motion Around Us provide clear, step-by-step answers to every exercise and in-text question from the chapter Describing Motion Around Us of the NCERT textbook Exploration. Prepared by subject experts as per the latest NCERT (CBSE) syllabus for 2026-27, these NCERT Solutions for Class 9 Science help you understand each concept, write exam-ready answers, and check your own solutions. You can read them online below or download the free Class 9 Science Chapter 4 question-answer PDF.
NCERT Solutions for Class 9 Science Chapter 4 Describing Motion Around Us
- Class: Class 9
- Subject: Science
- Chapter: Chapter 4 – Describing Motion Around Us
- Textbook: Exploration (NCERT)
- Study material: NCERT Solutions – questions with answers, free PDF
These solutions answer all the exercise questions of Chapter 4 Describing Motion Around Us — including the in-text questions, short-answer and long-answer questions, and activities — with complete explanations so you can follow the method, not just the final answer. Read the full solutions below.
NCERT Solutions Class 9 Science Chapter 4 Describing Motion Around Us View Download
NCERT Solutions for Class 9 Science Chapter 4 PDF Download
You can read the NCERT Solutions for Class 9 Science Chapter 4 online above, or download the complete question-answer PDF to study Describing Motion Around Us offline at any time.
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Questions Covered in This Chapter
These NCERT Solutions answer all 55 questions of this chapter. The questions solved are:
- How much distance should we maintain from the truck ahead to avoid a collision if it suddenly applies the brakes?
- Does this distance depend upon the speed with which we are moving?
- Can these quantities ever be equal?
- As shown in Fig. 4.5, a ball is thrown vertically upwards from O. It moves up straight till B and then falls back to O. Can this be considered a motion in a straight line?
- For this motion, fill up the values in Table 4.1.
- Analyse the data filled in Table 4.1 and choose which of the following is true for displacement: (i) It is never zero. (ii) Its magnitude can be greater than the total distance travelled. (iii) Its magnitude is less than or equal to the total distance travelled. (iv) Its magnitude is less than the total distance travelled in all cases.
- In the example of an athlete running back and forth on a straight track (Fig. 4.4), when will the displacement of the athlete be zero? What will be the total distance travelled in that case?
- Fuel used up in a vehicle depends on which of the following? Justify your answer. (i) Total distance travelled (ii) Displacement
- A ball rolls down an inclined track as shown in Fig. 4.6. Is its motion, a straight line motion? Assuming the starting point of the ball (O) to be the origin, can its motion from O to D be depicted using a horizontal line as shown in Fig. 4.3? Are the values of total distance travelled and magnitude of displacement from O equal or different at positions A, B, C and D?
- During a family road trip, you drive 200 km north in three hours. Afterwards, you drive 200 km south in two hours. Find the average speed and average velocity for your entire trip.
- Under what condition(s) is the (i) magnitude of average velocity of an object equal to its average speed? (ii) magnitude of average velocity of an object zero while its average speed is not zero?
- The magnitude of average acceleration of cars is generally specified as the time taken by the car to go from 0 km h⁻¹ to 100 km h⁻¹. Look it up on the internet and find this time for various cars, and record those in Table 4.2.
- Calculate the magnitude of average acceleration for each car.
- Refer to Table 4.3. We need to decide which quantity (time or position) to be shown along each axis.
- Determine a suitable scale for each quantity to represent it on the graph paper.
- Once all points are plotted, connect them to create the position-time graph for the vehicle's motion (Fig. 4.11c). It is a straight line for the data given in Table 4.3.
- What does the shape of the position-time graph indicate about the nature of motion?
- Which physical quantities can be obtained from a position-time graph?
- In the position-time graph we plotted (Fig. 4.11c), consider a part (say, AB) of the graph as shown in Fig. 4.14. From A, draw a line parallel to X-axis and another line parallel to Y-axis. Repeat the same from B.
- Extend the horizontal line from A and a triangle ABC is formed. What do the sides BC and CA of the triangle represent?
- As per Eq. (4.2a), by dividing the change in position (BC) by the change in time (CA), you get the average velocity.
- By extracting values of time t₁ and t₂, and distances s₁ and s₂ from the graph, the magnitude of average velocity can be calculated.
- What does the shape of the velocity-time graph indicate about the nature of motion?
- Which physical quantities can be obtained from a velocity-time graph?
- Can you calculate some other physical quantity from the velocity-time graph?
- Can you now understand why it is important to maintain a safe distance from the vehicle moving ahead of your vehicle (Fig. 4.20) and how this distance needs to be adjusted given your initial velocity?
- What is the distance travelled by the child? What is their displacement from their original position?
- What is the distance travelled by the child in making one revolution (going round the circle once)?
- In case of uniform circular motion, the speed is constant but what about the direction of velocity at an instant? Is it changing?
- Take a ring, such as an adhesive tape ring and one marble.
- Place the ring flat on a smooth surface and throw the marble inside the ring in a way that it rotates along the inner boundary of the ring (Fig. 4.24).
- Predict what will happen if you lift the ring while the marble is moving.
- Now, after one or two complete revolutions of the marble, pick up the ring without disturbing the motion of the marble. What do you observe? Does the marble continue moving in a circular motion? Or does it move in some other manner?
- Repeat the activity multiple times to confirm the result.
- My father went to a shop from home which is located at a distance of 250 m on a straight road. On reaching there, he discovered that he forgot to carry a cloth bag. He came home to take it, went to the shop again, bought provisions and came back home. How much was the total distance travelled by him? What was his displacement from home?
- A student runs from the ground floor to the fourth floor of a school building to collect a book and then comes down to their classroom on the second floor. If the height of each floor is 3 m, find: (i) the total vertical distance travelled, and (ii) their displacement from the starting point.
- A girl is riding her scooter and finds that its speedometer reading is constant. Is it possible for her scooter to be accelerating and if so, how?
- A car starts from rest and its velocity reaches 24 m s⁻¹ in 6 s. Find the average acceleration and the distance travelled in these 6 s.
- A motorbike moving with initial velocity 28 m s⁻¹ and constant acceleration stops after travelling 98 m. Find the acceleration of the motorbike and the time taken to come to a stop.
- Fig. 4.27 shows a position-time graph of two objects A and B that are moving along the parallel tracks in the same direction. Do objects A and B ever have equal velocity? Justify your answer.
- A graph in Fig. 4.28 shows the change in position with time for two objects A and B moving in a straight line from 0 to 10 seconds. Choose the correct option(s). (i) The average velocity of both over the 10 s time interval is equal since they have the same initial and final positions. (ii) The average speeds of both over the 10 s time interval are equal since both cover equal distance in equal time. (iii) The average speed of A over the 10 s time interval is lower than that of B since it covers a shorter distance than B in 10 seconds. (iv) The average speed of A over the 10 s time interval is greater than that of B since B's speed is lower than A's in some segments.
- A truck driver driving at the speed of 54 km h⁻¹ notices a road sign with a speed limit of 40 km h⁻¹ (Fig. 4.29) for trucks. He slows down to 36 km h⁻¹ in 36 s. What was the distance travelled by him during this time? Assume the acceleration to be constant while slowing down.
- A car starts from rest and accelerates uniformly to 20 m s⁻¹ in 5 seconds. It then travels at 20 m s⁻¹ for 10 seconds and finally applies the brake (with uniform acceleration) to stop in 6 seconds. Find the total distance travelled.
- A bus is travelling at 36 km h⁻¹ when the driver sees an obstacle 30 m ahead. The driver takes 0.5 seconds to react before pressing the brake. Once the brake is applied, the velocity of the bus reduces with constant acceleration of 2.5 m s⁻². Will the bus be able to stop before reaching the obstacle?
- A student said, “The Earth moves around the Sun”. In this context, discuss whether an object kept on the Earth can be considered to be at rest.
- The velocity-time graph from 0 s to 120 s for a cyclist is shown in Fig. 4.30. Shade the areas (in different colours) representing the displacement of the cyclist (i) while cyclist is moving with constant velocity. (ii) when the velocity of cyclist is decreasing. Also, calculate the displacement and average acceleration in the 120 s time interval.
- A girl is preparing for her first marathon by running on a straight road. She uses a smartwatch to calculate her running speed at different intervals. The graph (Fig. 4.31) depicts her velocity versus time. Estimate the distance she ran based on the graph.
- On entering a state highway, a car continues to move with a constant velocity of 6 m s⁻¹ for 2 minutes and then accelerates with a constant acceleration 1 m s⁻² for 6 seconds. Find the displacement of the car on the state highway in the 2 min 6 s time interval by drawing a velocity-time graph for its motion.
- Two cars A and B start moving with a constant acceleration from rest, in a straight line. Car A attains a velocity of 5 m s⁻¹ in 5 s. Car B attains a velocity of 3 m s⁻¹ in 10 s. Plot the velocity-time graphs for both the cars in the same graph. Using the graph, calculate the displacement in the two time intervals mentioned (Hint: Calculate the acceleration in both cases. Then calculate their velocities at five instants of time to plot the graph).
- Rohan studies science from 6 PM to 7:30 PM at home. Consider the tip of the minute's hand of the wall clock. During the given time interval, what is its: (i) distance travelled, (ii) displacement, (iii) speed, and (iv) velocity. The length of the minute's hand is 7 cm (Fig. 4.32).
- Take a cardboard disc (radius ~ 8 cm) (Fig. 4.33). Write numbers 1 to 12 on the outer part (7 cm from the centre) and the letters ‘ABCDEF’ on the inner part (4 cm from the centre), using the same font size. Spin the disc slowly, then faster, and observe how the numbers and letters appear. Why do the numbers fade or disappear while the letters remain visible? Are the speeds of the numbers and letters the same or different?
- Many smartphones have an inbuilt accelerometer that can detect very small accelerations. Install an app, such as Phyphox (phyphox.org) and open ‘Accelerometer (without g)’. Note the readings when (i) the phone is on an outstretched palm, and (ii) the phone is kept on the floor. What differences do you observe? What does this tell you about motion and acceleration in real situations? (Such tiny, involuntary movements are also studied in medical research, for example, in movement disorders) This activity is recommended to be performed as a classroom group activity facilitated by teacher.
- For motion in a straight line with constant acceleration, we derived two primary equations given by Eq. (4.4a) and (4.4b). Using these two equations, three more equations can be derived, out of which we derived one given in Eq. (4.4c). Derive the remaining two equations given below: s = vt − ½at² and s = ½(u + v)t. In mathematics, you have learnt the formula for calculating the area of a trapezium. Using that formula, derive the second equation given above.
- Plot graphs for data given in Table 4.4, using different X and Y scales, on different graph papers. Compare the graphs to find how the appearance of graph is affected by the choice of scales and decide which scale is better and why. Now repeat this with any graph plotting app. Such apps generally automatically adjust the axes to fit the data well on the screen.
- Talk to a motor mechanic about how a vehicle's braking or stopping distance is affected by: (i) wet roads, (ii) worn-out tyres, (iii) higher vehicle mass, (iv) driving at night, (v) fog, (vi) severe weather (rain, snow, storm), and (vii) driver reaction time. Using this information, design safety posters for your school and prepare a short skit to present it in the assembly.
Chapter at a Glance
- Position is the distance and direction of an object from a chosen reference point at a given instant. An object is in motion if its position changes with time; at rest if it does not.
- Total distance travelled counts the whole path; displacement is only the net change in position, and it needs a direction as well as a magnitude. Magnitude of displacement ≤ total distance travelled, always.
- Average speed = total distance travelled / time interval. Average velocity = displacement / time interval. Both have the SI unit m s⁻¹, but only velocity carries a direction.
- Average acceleration = change in velocity / time interval, SI unit m s⁻². It points along the velocity when the speed is rising and opposite to it when the speed is falling.
- On a position–time graph the slope is velocity: a straight line means constant velocity, a curve means accelerated motion. On a velocity–time graph the slope is acceleration and the area under the line is the displacement.
- For constant acceleration: v = u + at, s = ut + ½at², v² = u² + 2as. These three follow from the definitions, not from memory.
- In uniform circular motion the speed is constant but the direction of velocity (along the tangent) changes every instant — so the motion is accelerated. In one revolution the distance is 2πR and the displacement is zero.
How to Download NCERT Solutions for Class 9 Science Chapter 4 PDF
Follow these simple steps to get the Describing Motion Around Us questions-and-answers PDF from Exploration.
- Search NCERT Solutions for Class 9 Science Chapter 4 aglasem and open this page.
- Read the exercise questions with answers for Describing Motion Around Us shown above.
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NCERT Solutions for Class 9 Science – All Chapters
There are more chapters to study besides Describing Motion Around Us in Science. Here are the NCERT Solutions for all chapters of Class 9 Science.
- Chapter 1 Exploration Entering the World of Secondary Science
- Chapter 2 Cell the Building Block of Life
- Chapter 3 Tissues in Action
- Chapter 4 Describing Motion Around Us
- Chapter 5 Exploring Mixtures and Their Separation
- Chapter 6 How Forces Affect Motion
- Chapter 7 Work Energy and Simple Machines
- Chapter 8 Journey Inside the Atom
- Chapter 9 Atomic Foundations of Matter
- Chapter 10 Sound Waves Characteristics and Applications
- Chapter 11 Reproduction How Life Continues
- Chapter 12 Patterns in Life Diversity and Classification
- Chapter 13 Earth As a System Energy Matter and Life
NCERT Solutions for Class 9 – All Subjects
Just like Chapter 4 of Science, you can get the exercise questions with answers for every other subject of Class 9. Here are the NCERT Solutions for all subjects of Class 9.
NCERT Solutions for Class 9 Science Chapter 4 – An Overview
The key highlights of this study material are as follows.
| Aspects | Details |
|---|---|
| Class | Class 9 |
| Subject | Science |
| Chapter Number | Chapter 4 |
| Chapter Name | Describing Motion Around Us |
| Book Name | Exploration |
| Book By | NCERT (National Council of Educational Research and Training) |
| Educational Resource Here | NCERT Solutions of Class 9 Science Chapter 4 for all exercises |
| More Questions Answers of This Subject | NCERT Solutions for Class 9 Science |
| Download Book Chapter | NCERT Book Class 9 Science |
| All Questions Answers For This Class | NCERT Solutions for Class 9 |
| Complete Solutions | NCERT Solutions |
NCERT Solutions for Class 9 Science Chapter 4 Describing Motion Around Us – FAQs
What are the NCERT Solutions for Class 9 Science Chapter 4 Describing Motion Around Us?
They are the complete, step-by-step answers to all the exercise and in-text questions of Chapter 4 Describing Motion Around Us from the NCERT Class 9 Science textbook Exploration, written by experts as per the latest NCERT syllabus.
How can I download the Class 9 Science Chapter 4 solutions PDF for free?
Open this page on aglasem, read the Describing Motion Around Us questions with answers, and click the “Download Solutions PDF” link. The Class 9 Science Chapter 4 NCERT Solutions PDF is completely free to download.
Are these NCERT Solutions as per the latest 2026-27 syllabus?
Yes. The NCERT Solutions for Class 9 Science Chapter 4 are based on the latest NCERT textbook Exploration and the current 2026-27 CBSE syllabus, so the questions and answers match what you study in class.
Where can I get NCERT Solutions for the other chapters of Class 9 Science?
You can find the answers to every chapter on the NCERT Solutions for Class 9 Science page, and solutions for every subject on the NCERT Solutions for Class 9 page.
How do NCERT Solutions help in exam preparation?
They show the correct method to solve each question, help you write answers the way they are expected in exams, let you check and correct your own work, and save revision time — which together improve your marks in Class 9 Science.
If you have any queries on NCERT Solutions for Class 9 Science Chapter 4 Describing Motion Around Us, then please ask in the comments below.
