NCERT Solutions for Class 9 Science Chapter 8 Motion: Download Free PDF

NCERT Solution for Class 9 Science Chapter 8 Motion: Aakash Institute has designed the Solutions for Chapter 8 Motion to quickly clarify doubts and concepts for all students. Class 9 solutions in Science are a valuable reference and guiding hand, which helps students in clearing doubts instantly and effectively. Aakash Solutions for Class 9 Science approaches students in an effective way and is packed with questions, activities, and board and competitive exam-oriented exercises.

NCERT solutions for Class 9 Science PDF is the contribution of the faculty having excellent teaching experience. It has been prepared to target a concept-based approach along with the precise answering way for examinations. Refer to Aakash Solutions for Class 9 for better scores on the internet and year-end assessments exams. It is a well-structured solution for a reliable format of the concept-based learning experience.

Motion, in Physics, changes the position or direction of a body over time. The translation is considered displacement around a line or a curve. The motion that adjusts a body's direction is called rotation. Both points in the body have the same velocity-directed velocity and the same velocity-change acceleration time rate in all situations. Both translation and rotation combine the most common kind of motion. Both movements are relative to a reference point. To state that a body is at rest, which implies that it is not in motion, clearly implies that it is defined as a frame of reference that moves with the body.

Students will study some of the basic and most important concepts of physics in this chapter. which include uniform and non-uniform motion, distance and displacement, speed, velocity, unit of speed, and acceleration.

This chapter also teaches students about the:

1. difference between average speed and velocity

2. difference between acceleration and velocity

3. difference between speed and velocity

4. newton's law of motion. 

Class 9 Science Chapter 8 Motion Video

NCERT Solution for Class 9 Science Chapter 8 - Motion Question and Answers PDF

NCERT Solutions for Class 9 Science Chapter 8 Motion

Topic 8.1 Describing Motions

Q 1. An object has moved through a distance. Can it have zero displacements? If yes, support your answer with an example.

Answer:

Yes, an object that has moved through a distance can have zero displacements.

If an object moves and returns to the original position, the displacement will be zero. Consider the movement in a circular path. A man walks from point A in a circular path in a park and comes back to point A.

The distance traveled is equal to the circumference of the circular path, but displacement is zero.

Q 2. A farmer moves along the boundary of a square field of side 10 m in 40 s. What will be the magnitude of displacement of the farmer at the end of 2 minutes 20 seconds from his initial position? 

Answer:

Now, 

Q 3. Which of the following is true for displacement?

(a) It cannot be zero.

(b) Its magnitude is greater than the distance traveled by the object.

Answer:

(a) The first statement is false. Because displacement can be zero when the initial point coincides with the final point.

(b) The second statement is false. The magnitude of displacement can never be greater than the distance traveled by the object. It can be either equal or less.

Topic 8.2 Measuring the Rate of Motion

Q 1. Distinguish between speed and velocity.

Answer:

Q 2. Under what condition(s) is the magnitude of the average velocity of an object equal to its average speed? 

Answer: When the total distance traveled by the object is equal to the displacement, the magnitude of the average velocity will be equal to the average speed. Average speed is the total distance upon the time taken, whereas average velocity is the total displacement upon time taken.

Q 3. What does the odometer of an automobile measure?

Answer: Odometer is a device that measures the total distance traveled by automobile.

Q 4. What does the path of an object look like when it is in uniform motion?

Answer: An object is having a uniform motion if it covers equal distance in equal interval of time (which implies speed is constant!). So the path can be straight or curved.

For eg. Consider a circular path. For understanding purposes, divide the circumference of the circle in six equal parts each subtending at the centre. The object covers each equal part in equal amounts of time. Hence, by definition, this object is in uniform motion.

Q 5. During an experiment, a signal from a spaceship reached the ground station in five minutes. What was the distance of the spaceship from the ground station? The signal travels at the speed of light, that is , .

Answer:

Topic 8.3 Rate of Change of Velocity 

Q 1. When will you say a body is in

(i) uniform acceleration?

(ii) nonuniform acceleration?

Answer:

(i) If the velocity of an object traveling in a straight line increases or decreases by equal amounts in equal intervals of time, then the acceleration of the object is said to be uniform. For example, An apple having a free-fall motion.

(ii) On the other hand, if the velocity of the object increases or decreases by unequal amounts in equal intervals of time, then the acceleration of the object is said to be non-uniform. For example, A car traveling along a straight road increases its speed by unequal amounts in equal intervals of time.

Q.2 A bus decreases its speed from 80 km h -1 to 60 km h -1 in 5 s. Find the acceleration of the bus.

Answer:

Q 3 . A train starting from a railway station and moving with uniform acceleration attains a speed 40 km h _-1 in 10 minutes. Find its acceleration.

Topic 8.4 Graphical Representation of Motion

Q 1. What is the nature of the distance-time graphs for uniform and non-uniform motion of an object?

Answer:

Distance-time graph is the plot of distance traveled by an object along x-axis against time along y-axis.

For the uniform motion of an object, the distance-time graph is a straight line with a constant slope. (Note: However, the path may be straight or curved!)

For non-uniform motion of an object, the distance-time graph is a curved line with an increasing or decreasing slope.
 

Q2. What can you say about the motion of an object whose distance-time graph is a straight line parallel to the time axis?

Answer: 

If the distance-time graph of an object is a straight line parallel to the time axis, it means that the distance of the object is the same from its initial position at any point of time.

This implies that the object is not moving and is at rest.

Q3 . What can you say about the motion of an object if its speed time graph is a straight line parallel to the time axis?

Answer:

If the speed-time graph of an object is a straight line parallel to the time axis, it means that the speed of the object is not changing with time. Hence the speed of the object is constant. This also implies that the acceleration of the object is zero.

Q4. What is the quantity which is measured by the area occupied below the velocity- time graph?

Answer:

The area occupied below the velocity-time graph denotes the total distance traveled by an object in the given time frame.

 We know, 

Topic 8.5 Equations of Motion by Graphical Method

Q1.(a) A bus starting from rest moves with a uniform acceleration of 0.1 m s -2 for 2 minutes. Find

1. the speed acquired

Answer:

Q1.(b) A bus starting from rest moves with a uniform acceleration of 0.1 m s-2 for 2 minutes. Find

2. The distance traveled.

 Answer:

Q2. A train is traveling at a speed of 90 km h-1. Brakes are applied so as to produce a uniform acceleration of – 0.5 m s -2 . Find how far the train will go before it is brought to rest.

Answer:

Q3. A trolley, while going down an inclined plane, has an acceleration of 2 cm s -2 . What will be its velocity 3 s after the start?

Answer:

Q4. A racing car has a uniform acceleration of 4 m s -2 . What distance will it cover in 10 s after start?

Q 5. A stone is thrown in a vertically upward direction with a velocity of . If the acceleration of the stone during its motion is in the downward direction, what will be the height attained by the stone and how much time will it take to reach there?

Answer:

NCERT Solutions for class 9 science chapter 8 Motion: Solved Exercise Questions

Q 1. An athlete completes one round of a circular track of diameter 200 m in 40 s. What will be the distance covered and the displacement at the end of 2 minutes 20 s? 

Answer:

Q2. Joseph jogs from one end A to the other end B of a straight 300 m road in 2 minutes 30 seconds and then turns around and jogs 100 m back to point C in another 1 minute. What are Joseph’s average speeds and velocities in jogging.

(a) from A to B and
 

(b) from A to C? 

Answer:

Given,

 (a) Distance between A and B = 300m

(b) Distance traveled from A to reach C = And, Displacement from A to C =

 Q 3. Abdul, while driving to school, computes the average speed for his trip to be . On his return trip along the same route, there is less traffic and the average speed is   . What is the average speed for Abdul’s trip?

Answer:

Q 4. A motorboat starting from rest on a lake accelerates in a straight line at a constant rate of 8.0 s. How far does the boat travel during this time?

Answer:

Q 5. A driver of a car traveling at 52 km h -1 applies the brakes and accelerates uniformly in the opposite direction. The car stops in 5 s. Another driver going at 3 km h - 1 in another car applies his brakes slowly and stops in 10 s. On the same graph paper, plot the speed versus time graphs for the two cars. Which of the two cars traveled farther after the brakes were applied?

Answer:

Q 6. (a) Figure shows the distance-time graph of three objects A,B and C. Study the graph and answer the following questions:

• Which of the three is traveling the fastest?

Answer:

Given is a distance-time graph. The slope of this graph gives us speed. Hence, the graph with the highest slope will have the highest speed.

Since B has the highest slope(inclination), it travels the fastest.

Q 6. (b) Figure shows the distance-time graph of three objects A,B and C. Study the graph and answer the following questions:

• Are all three ever at the same point on the road?

Answer:

Given is a distance-time graph. Any point on the curve will give the distance of the object from O. Since there is no intersection point of all the three graphs, they never meet at the same point on the road.

(Although any two of them do meet at some point on the road!)

Q 6.(c) Figure shows the distance-time graph of three objects A,B and C. Study the graph and answer the following questions:

• How far has C traveled when B passes A?

Answer :

Given is a distance-time graph. Any point on the curve will give the distance of object from O. To find how far C has traveled when B passes A, draw a perpendicular from the intersection point of A and B on the time axis. The point where it intersects on the C graph, from C draws a perpendicular to y axis . Therefore, distance traveled by C will be (Final distance from O - Initial distance from O).

Therefore, C has traveled 6.5 km when B passes A. 

Q 6. (d) Figure shows the distance-time graph of three objects A,B and C. Study the graph and answer the following questions:

• How far has B traveled by the time it passes C?

 Answer:

Given is a distance-time graph. The graph of B and C intersect at a point whose y- coordinate is 5. Hence, B has traveled by the time it passes C.

Q 7. A ball is gently dropped from a height of 20 m. If its velocity increases uniformly at the rate of 10 m s -2 , with what velocity will it strike the ground? After what time will it strike the ground?

Answer:

Q 8.(a) The speed-time graph for a car is shown is Figure:

Find how far does the car travel in the first 4 seconds. Shade the area on the graph that represents the distance traveled by the car during the period. 

Answer:

Given is a speed-time graph. The area under the curve will give the distance traveled by the car.

 Q 8. (b) The speed-time graph for a car is shown is Figure:

Which part of the graph represents uniform motion of the car?

Q 9. (a) State which of the following situations are possible and give an example for each of these:

• an object with a constant acceleration but with zero velocity

Answer:

(a) The given situation is possible.

 When an object is thrown upwards (under gravity only), it reaches a maximum height where its velocity becomes zero. However, it still has an acceleration acting in the downward direction (acceleration due to gravity).

 Note: This is possible for a given point of time, however, it is not possible for a period of time.

Q 9.(b) State which of the following situations are possible and give an example for each of these:

• an object moving with an acceleration but with uniform speed.

Answer:

(b) The given situation is possible.

An object moving in a circular path with uniform speed, i.e covering equal distance in equal amount of time is still under acceleration. Because, the velocity keeps on changing due to continuous change in the direction of motion. Therefore, circular motion is an example of an object moving with an acceleration but with uniform speed.

Q 9. (c) State which of the following situations are possible and give an example for each of these:

• an object moving in a certain direction with an acceleration in the perpendicular direction.

Answer:

(c) The given situation is possible.

For an object moving in a circular path with constant speed, the direction of its velocity at any point will be tangential to that point. However, its acceleration will be directed radially inwards. (Constant speed but still having an acceleration - Due to continuous change in direction.)

Q 10. An artificial satellite is moving in a circular orbit of radius 42250 km. Calculate its speed if it takes 24 hours to revolve around the earth.

Answer:

Motion Important Question and Answers

Q1. What is Motion in Physics?
Answer: Motion in physics refers to the change in the position of an object over time. It is observed with respect to a frame of reference and is described in terms of displacement, distance, speed, velocity, and acceleration.

Q2. What are the Types of Motion?
Answer: There are three main types of motion:

• Translational Motion: Movement in a straight or curved path, like a car driving on a road.
• Rotational Motion: Movement around a fixed point, like a spinning top.
• Oscillatory Motion: Back-and-forth movement, like a pendulum.

Q3. What is the Difference Between Distance and Displacement?
Answer: Distance is the total path covered by an object, regardless of direction. Displacement is the shortest straight-line distance from the starting point to the endpoint, considering direction.

Q4. How Do You Define Speed and Velocity?
Answer: Speed is the rate at which an object moves, without regard for direction. Velocity includes both the speed and the direction of motion. For example, 60 km/h north is a velocity, while 60 km/h alone is speed.

Q5. What is Acceleration in Physics?
Answer: Acceleration is the rate of change of velocity over time. It can be positive (speeding up) or negative (slowing down), depending on whether the object's velocity increases or decreases.

FAQs for Class 9 Science NCERT Solutions
 

Q. Where to download the NCERT solutions for class 9th Science?

A. Aakash provides the chapter-wise solutions of NCERT for class 9th in Science, and they are available on the Aakash website. The solutions are in order and chapter-wise. They have been consolidated into just one PDF file.

Q. How would I score excellent marks in Science class 9?

A. The best way to score more marks in the CBSE Class 9 Science Test is through sheer practice and theory from the textbook. The solutions help you in the context of practice. It is an ideal approach to scoring well in tests.

Q. What is an ideal textbook for Class 9 Science CBSE?

A. An ideal textbook for Class 9 Science is NCERT. Do not merely mug up the ideas; instead examine and understand all the ideas entirely. Create notes and practice as much as possible.

Q. What are the best tips to use the NCERT solutions for Class 9 Science?

A. The best tips to assist you in using NCERT Solutions for Class 9 Science are following:

1. Go through the NCERT syllabus from the NCERT textbook to cover the theory portion.

2. Practise the questions by taking the help of the NCERT solutions provided by Aakash institute.

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A. All the questions that are included in CBSE Exams are based on the NCERT Class 9. Thus, in order to get good marks, it is necessary to be well-versed with all the questions covered in Class 9 NCERT Solutions that can only be achieved through regular practice.

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