#### Chapters

#### Lakhmir Singh Science Class 9 Part 1 Physics

## Chapter 1 : Motion

#### Pages 19 - 22

Is displacement a scalar quantity ?

State whether distance is a scalar or a vector quantity.

Change the speed of 6 m/s into km/h.

What name is given to the speed in a specified direction ?

Give two examples of bodies having non-uniform motion.

Name the physical quantity obtained by dividing ‘Distance travelled’ by ‘Time taken’ to travel that distance.

What do the following measure in a car ?

(a) Speedometer (b) Odometer

Name the physical quantity which gives us an idea of how slow or fast a body is moving.

Under what conditions can a body travel a certain distance and yet its resultant displacement be zero ?

In addition to speed, what else should we know to predict the position of a moving body ?

When is a body said to have uniform velocity ?

Under which condition is the magnitude of average velocity equal to average speed ?

Which of the two can be :zero under certain conditions : average speed of a moving body or average velocity of a moving body ?

Give one example of a situation in which a body has a certain average speed but its average velocity is zero.

What is the acceleration of a body moving with uniform velocity ?

What is the other name of negative acceleration ?

Name the physical quantity whose SI unit is :

(a) m/s (b) m/s^{2}

What type of motion is exhibited by a freely falling body ?

What is the SI unit of retardation ?

Fill in the following blank with suitable word :

Displacement is a…………………… quantity whereas distance is a………………………….

Fill in the following blank with suitable word:

The physical quantity which gives both, the speed and direction of motion of a body is called its……………

Fill in the following blank with suitable word :

A motorcycle has a steady……………. of 3 m/s^{2}. This means that every………………. its…………….. increases by………….

Fill in the following blank with suitable word :

Velocity is the rate of change of……………………… It is measured in .

Fill in the following blank with suitable word :

Acceleration is the rate of change of………………. It is measured in.

What type of motion, uniform or non-uniform, is exhibited by a freely falling body ? Give reason for your answer.

State whether speed is a scalar or a vector quantity. Give reason for your choice.

Bus X travels a distance of 360 km in 5 hours whereas bus Y travels a distance of 476 km in 7 hours. Which

bus travels faster ?

Arrange the following speed in increasing order (keeping the least speed first):

An athlete running with a speed of 10 m/s.

Arrange the following speed in increasing order (keeping the least speed first):

A bicycle moving with a speed of 200 m/min.

Arrange the following speed in increasing order (keeping the least speed first

A scooter moving with a speed of 30 km/h.

Write the formula for acceleration. Give the meaning of each symbol which occurs in it.

A train starting from Railway Station attains a speed of 21 m/s in one minute. Find its acceleration.

What term is used to denote the change of velocity with time ?

Give one word which means the same as ‘moving with a negative acceleration’.

The displacement of a moving object in a given interval of time is zero. Would the distance travelled by the object also be zero ? Give reason for your answer.

A snail covers a distance of 100 metres in 50 hours. Calculate the average speed of snail in km/h.

A tortoise moves a distance of 100 metres in 15 minutes. What is the average speed of tortoise in km/h ?

If a sprinter runs a distance of 100 metres in 9.83 seconds, calculate his average speed in km/h.

A motorcyclist drives from place A to B with a uniform speed of 30 km h^{-1} and returns from place B to A with a uniform speed of 20 km h^{-1}. Find his average speed.

A motorcyclist starts from rest and reaches a speed of 6 m/s after travelling with uniform acceleration for 3 s. What is his acceleration ?

An aircraft travelling at 600 km/h accelerates steadily at 10 km/h per second. Taking the speed of sound as 1100 km/h at the aircraft’s altitude, how long will it take to reach the ‘sound barrier’ ?

If a bus travelling at 20 m/s is subjected to a steady deceleration of 5 m/s^{2}, how long will it take to come to rest ?

What is the difference between distance travelled by a body and its displacement ? Explain with the

help of a diagram.

An ant travels a distance of 8 cm from P to Q and then moves a distance of 6 cm at right angles to PQ. Find its resultant displacement.

Define motion. What do you understand by the terms uniform motion and non-uniform motion ? Explain with examples.

Define speed. What is the SI unit of speed ?

What is meant by uniform speed ?

What is meant by average speed?

Define velocity. What is the SI unit of velocity ?

Distinguish between speed and velocity.

Convert a speed of 54 km/h into m/s.

What is meant by the term acceleration ? State the SI unit of acceleration.

Define the term uniform acceleration. Give one example of a uniformly accelerated motion.

The distance between Delhi and Agra is 200 km. A train travels the first 100 km at a speed of 50 km/h. How fast must the train travel the next 100 km, so as to average 70 km/h for the whole journey ?

A train travels the first 15 km at a uniform speed of 30 km/h; the next 75 km at a uniform speed of 50 km/h; and the last 10 km at a uniform speed of 20 km/h. Calculate the average speed for the entire train journey.

A car is moving along a straight road at a steady speed. It travels 150 m in 5 seconds:

What is its average speed ?

A car is moving along a straight road at a steady speed. It travels 150 m in 5 seconds:

How far does it travel in 1 second ?

A car is moving along a straight road at a steady speed. It travels 150 m in 5 seconds:

How far does it travel in 6 seconds ?

A car is moving along a straight road at a steady speed. It travels 150 m in 5 seconds:

How long does it take to travel 240 m ?

A body is moving along a circular path of radius R. What will be the distance travelled and displacement of the body when it completes half a revolution ?

If on a round trip you travel 6 km and then arrive back home :

What distance have you travelled ?

If on a round trip you travel 6 km and then arrive back home :

What is your final displacement ?

A body travels a distance of 3 km towards East, then 4 km towards North and finally 9 km towards East.

What is the total distance travelled ?

A body travels a distance of 3 km towards East, then 4 km towards North and finally 9 km towards East.

What is the resultant displacement ?

A boy walks from his classroom to the bookshop along a straight corridor towards North. He covers a distance of 20 m in 25 seconds to reach the bookshop. After buying a book, he travels the same distance in the same time to reach back in the classroom. Find (a) average speed, and (b) average velocity, of the boy.

A car travels 100 km at a speed of 60 km/h and returns with a speed of 40 km/h. Calculate the average speed for the whole journey.

A ball hits a wall horizontally at 6.0 m s^{-1}. It rebounds horizontally at 4.4 m s^{-1}. The ball is in contact with the wall for 0.040 s. What is the acceleration of the ball ?

#### Pages 39 - 44

What remains constant in uniform circular motion ?

What changes continuously in uniform circular motion ? ‘

State whether the following statement is true or false :

Earth moves round the sun with uniform velocity.

A body goes round the sun with constant speed in a circular orbit. Is the motion uniform or accelerated ?

What conclusion can you draw about the velocity of a body from the displacement-time graph shown below :

Name the quantity which is measured by the area occupied under the velocity-time graph.

What does the slope of a speed-time graph indicate ?

What does the slope of a distance-time graph indicate ?

Give one example of a motion where an object does not change its speed but its direction of motion changes continuously.

Name the type of motion in which a body has a constant speed but not constant velocity.

What can you say about the motion of a body if its speed-time graph is a straight line parallel to the time axis ?

What conclusion can you draw about the speed of a body from the following distance-time graph ?

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

What conclusion can you draw about the acceleration of a body from the speed-time graph shown below .

A satellite goes round the earth in a circular orbit with constant speed. Is the motion uniform or accelerated ?

What type of motion is represented by the tip of the ‘seconds’ hand’ of a watch ? Is it uniform or accelerated ?

Fill in the following blank with suitable word :

If a body moves with uniform velocity, its acceleration is ..............

Fill in the following blank with suitable word :

The slope of a distance-time graph indicates ………………….. of a moving body.

Fill in the following blank with suitable word :

The slope of a speed-time graph of a moving body gives its………………………..

Fill in the following blank with suitable word :

In a speed-time graph, the area enclosed by the speed-time curve and the time axis gives the…………….. by the body.

Fill in the following blank with suitable word :

It is possible for something to accelerate but not change its speed if it moves in a………………………..

Is the uniform circular motion accelerated ? Give reasons for your answer

Write the formula to calculate the speed of a body moving along a circular path. Give the meaning of each symbol which occurs in it.

Explain why, the motion of a body which is moving with constant speed in a circular path is said to be accelerated.

What is the difference between uniform linear motion and uniform circular motion ? Explain with examples.

State an important characteristic of uniform circular motion. Name the force which brings about uniform circular motion.

Find the initial velocity of a car which is stopped in 10 seconds by applying brakes. The retardation due to brakes is 2.5 m/s^{2}.

Describe the motion of a body which is accelerating at a constant rate of 10 m s^{–}^{2}. If the body starts from rest, how much distance will it cover in 2 s ?

A motorcycle moving with a speed of 5 m/s is subjected to an acceleration of 0.2 m/s^{2}. Calculate the speed of the motorcycle after 10 seconds, and the distance travelled in this time.

A bus running at a speed of 18 km/h is stopped in 2.5 seconds by applying brakes. Calculate the retardation produced.

A train starting from rest moves with a uniform acceleration of 0.2 m/s^{2} for 5 minutes. Calculate the speed acquired and the distance travelled in this time.

Name the two quantities, the slope of whose graph give speed .

Name the two quantities, the slope of whose graph give acceleration.

A cheetah starts from, rest, and accelerates at 2 m/s^{2} for 10 seconds. Calculate :

(a) the final velocity

(b) the distance travelled.

A train travelling at 20 m s^{-1} accelerates at 0.5 m s^{-2 }for 30 s. How far will it travel in this time ?

A cyclist is travelling at 15 m s^{-1}. She applies brakes so that she does not collide with a wall 18 m away. What deceleration must she have ?

Draw a velocity-time graph to show the following motion :

A car accelerates uniformly from rest for 5 s ; then it travels at a steady’ velocity for 5 s.

The velocity-time graph for part of a train journey is a horizontal straight line. What does this tell you about the trains velocity.

The velocity-time graph for part of a train journey is a horizontal straight line. What does this tell you about its acceleration ?

Explain the meaning of the following equation of motion :v = u + at, where symbols have their usual meanings.

A body starting from rest travels with uniform acceleration. If it travels 100 m in 5 s, what is the value of acceleration ?

Derive the formula : v = u + at, where the symbols have usual meanings.

A bus was moving with a speed of 54 km/h. On applying brakes it stopped in 8 seconds. Calculate the acceleration.

Derive the formula s= `ut+1/2at^2` , where the symbols have usual meanings.

A train starting from stationary position and moving with uniform acceleration attains a speed of 36 km per hour in 10 minutes. Find its acceleration.

Write the three equation of uniformly accelerated motion. Give the meaning of symbol which occurs in them.

A car acquire a velocity of 72 km per hour in 10 second starting from rest. Find

(1) the acceleration,

(2) the average velocity, and

(3) the distance travelled in this time.

Give two examples of uniform circular motion.

What is meant by uniform circular motion ?

he tip of seconds’ hand of a dock takes 60 seconds to move once on the circular dial of the clock. If the radius of the dial of the clock be 10.5 cm, calculate the speed of the tip of the seconds’ hand of the clock. `(Given π= 22/7)`.

Show by means of graphical method that: v = u + at, where the symbols have their usual meanings.

Show by using the graphical method that: `s=ut+1/2at^2` where the symbols have their usual meanings.

Derive the following equation of motion by the graphical method : v^{2} = u^{2} + 2as, where the symbols have their usual meanings.

The graph given alongside shows the positions of a body at different times. Calculate the speed of the body as it moves from :

(1) A to B,

(2) B to C, and

(3) C to D.

What can you say about the motion of a body if:

its displacement-time graph is a straight line ?

What can you say about the motion of a body if:

its velocity-time graph is a straight line ?

A body with an initial velocity x moves with a uniform acceleration y. Plot its velocity-time graph.

Given alongside is the velocity-time graph for a moving body :

Find :

(i) Velocity of the body at point C.

(ii) Acceleration acting on the body between A and

(iii) Acceleration acting on the body between B and C.

A body is moving uniformly in a straight line with a velocity of 5 m/s. Find graphically the distance covered by it in 5 seconds.

The speed-time graph of an ascending passenger lift is given alongside.

What is the acceleration of the lift:

(1) during the first two seconds ?

(2) between second and tenth second ?

(3) during the last two seconds ?

A car is moving on a straight road with uniform acceleration. The speed of the car varies with time as follows :

Time (s) : 0 2 4 6 8 10

Speed (m/s) : 4 8 12 16 20 24

Draw the speed-time graph by choosing a convenient scale. From this graph :

(1) Calculate the acceleration of the car.

(2) Calculate the distance travelled by the car in 10 seconds.

The graph given alongside shows how the speed of a car changes with time:

(i) What is the initial speed of the car ?

(ii) What is the maximum speed attained by the car ?

(iii) Which part of the graph shows zero acceleration ?

(iv) Which part of the graph shows varying retardation ?

(v) Find the distance travelled in first 8 hours.

Three speed-time graphs are given below :

Which graph represents the case of:

(i) a cricket ball thrown vertically upwards and returning to the hands of the thrower ?

(ii) a trolley decelerating to a constant speed and then accelerating uniformly ?

Study the speed-time graph of a car given alongside and answer the following questions:

(i) What type of motion is represented by OA ?

(ii) What type of motion is represented by AB ?

(iii) What type of motion is represented by BC ?

(iv) What is the acceleration of car from O to A ?

(v)What is the acceleration of car from A to B ?

(vi) What is the retardation of car from B to C ?

What type of motion is represented by the following graph ?

What type of motion is represented by the following graph ?

What type of motion is represented by the following graph ?

What type of motion is represented by the following graph ?

A car is travelling along the road at 8 ms^{-1}. It accelerates at 1 ms^{-2} for a distance of 18 m. How fast is it then travelling ?

A car is travelling at 20 m/s along a road. A child runs out into the road 50 m ahead and the car driver steps on the brake pedal. What must the car’s deceleration be if the car is to stop just before it reaches the child ?

#### Lakhmir Singh Science Class 9 Part 1 Physics

#### Textbook solutions for Class 9

## Lakhmir Singh solutions for Class 9 Science chapter 1 - Motion

Lakhmir Singh solutions for Class 9 Science chapter 1 (Motion) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CBSE Science for Class 9 Part 1 Physics solutions in a manner that help students grasp basic concepts better and faster.

Further, we at shaalaa.com are providing such solutions so that students can prepare for written exams. Lakhmir Singh textbook solutions can be a core help for self-study and acts as a perfect self-help guidance for students.

Concepts covered in Class 9 Science chapter 1 Motion are Motion (Numerical), Uniform Circular Motion, Derivation of Equations of Motion by Graphical Method, Graphical Representation of Motion - Distance-time Graphs, Describing Motion - Uniform Motion and Nonuniform Motion, Motion (Introduction), Describing Motion - Motion Along a Straight Line, Measuring the Rate of Motion - Speed with Direction, Rate of Change of Velocity, Graphical Representation of Motion - Velocity-time Graphs, Equations of Motion by Graphical Method - Equation for Velocity-time Relation, Equations of Motion by Graphical Method - Equation for Position-time Relation, Equations of Motion by Graphical Method - Equation for Position-velocity Relation, Distance and Displacement.

Using Lakhmir Singh Class 9 solutions Motion exercise by students are an easy way to prepare for the exams, as they involve solutions arranged chapter-wise also page wise. The questions involved in Lakhmir Singh Solutions are important questions that can be asked in the final exam. Maximum students of CBSE Class 9 prefer Lakhmir Singh Textbook Solutions to score more in exam.

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