# Samacheer Kalvi 9th Science Book Back Answers Chapter 2

## Samacheer Kalvi 9th Science Book Back Question and Answers:

Samacheer Kalvi 9th Standard Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 9 New Syllabus 2022 to 2023 Book Back Questions & Answers/solutions available for both English and Tamil Medium. Class 9 std Science Book Term 1 Chapter 2  – Motions Answers/Solutions Guide are uploaded on this page. In new 9th Science syllabus Term 1, Term 2, Term 3 are combined into a single book. 9th standard Science Book is consists of 25 Units. All 25 chapters of Term 1st, 2nd, 3rd Science Book Back One, and Two Mark Solutions are given below.

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### 9th Science Book Back Term 1 Chapter 2 Solutions Guide PDF:

Samacheer Kalvi 9th Science Subject 1 Mark and 2 Mark Solutions Guide PDF available below. Click the Download option to download the book back 1 Mark & 2 Mark questions and answers. Take the printout and use it for exam purposes.

### Motions – Book Back Answers

I. Multiple choice questions:

1. Slope of the velocity – time graph – gives
a) Speed
b) Displacement
c) Distance
d) Acceleration

2. Which of the following graph represents uniform motion of a moving particle?

Ans: b

3.A body moving with an initial velocity 5ms-1 and accelerates at 2ms-1. Its velocity after 10s is
a) 20ms-1
b) 25ms-1
c) 5ms-1
d) 22.55ms-1

4. In a 100m race, the winner takes 10s to reach the finishing point. The average speed of the winner is
a) 5ms-1
b) 20ms-1
c) 40ms-1
d) 10ms-1

5. The area under velocity – time graph represents
a) Velocity of the moving object.
b) Displacement covered by the moving object
c) Speed of the moving object
d) Accewinlm een.ceom ration of the moving object

6. A car is being driven at a speed of 20ms-1 when brakes are applied to bring it to rest in 5s. the deceleration produced in this case will be
a) +4ms-2
b) -4ms-2
c) -0.2ms-2
d) +0.25ms-2

7. Unit of acceleration is
a) ms-7
b) ms-2
c) ms
d) ms2

8. Which one of the following is most likely not a case of uniform circular motion?
a) Motion of the earth around the sun
b) Motion of a toy train on a circular track.
c) Motion of a racing car on a circular track.
d) Motion of hours hand on the dial of the clock.

9. The force responsible for drying of clothes in a washing machine is
a) Centripetal force
b) Centrifugal force
c) Gravitational force
d) Electro static force

10. The centrifugal force is
a) Real force
b) The force of reaction of centripetal force
c) Virtual force
d) Directed towards the centre of the circular path.

11. When a body starts from rest the acceleration of the body after 2 second is Of its
displacement.
a) Half
b) Twice
c) Four times
d) Once fourth

12. In a 100m race, the winner takes 10s to reach the finishing point. The average speed of the winner is
………………… ms-1
a) 5
b) 10
c) 20
d) 40

II. Fill in the blanks

1. Speed is a Scalar quantity whereas velocity is a Vector quantity.
2. The slope of the distance – time graph at any point gives Speed
3. Consider an object is rest at position x = 20m, Then its displacement – time graph will be straight line to Parallel
4. Negative acceleration is called retardation (or) deceleration
5. Area under velocity – time graph shows the distance (or) magnitude of displacement

III. True of False

1. The motion of a city bus in a heavy traffic road is an example for uniform motion. – False
2. Acceleration can get negative value also.- True
3. Distance covered by a particle never becomes zero between any interval of time bur displacement becomes zero. – True
4. The velocity – time graph of a particle falling freely under gravity would be straight line parallel to the x axis. – False
5. If the velocity – time graph of a particle is a straight line inclined to time axis then its displacement – time graph will be a straight line? – True

IV. Assertion and Reason Type question

Make the correct choice as:
a) If both assertion and reason are true and reason is the correct explanation of assertion.
b) If both assertion and reason are true but reason is not the correct explanation of assertion.
c) If assertion is true but reason is false.
d) If assertion is false but reason is true.

1. Assertion: The accelerated motion of an object may be due to change in magnitude of velocity or direction or both of them.
Reason: Acceleration can be produced only by change in magnitude of the velocity it does not depend on the direction.
Ans: c) If assertion is true but reason is false.

2. Assertion: The speedometer of a car or a motor-cycle measured the average speed of it Reason: Average velocity is equal to total displacement divided by total time taken.
Ans: b) If both assertion and reason are true but reason is not the correct explanation of assertion.

3. Assertion: Displacement of a body may be zero when distance travelled by it is not zero. Reason: The displacement is the shortest distance between initial and final position.
Ans: a) If both assertion and reason are true and reason is the correct explanation of assertion

V. Match the Following

Ans: 1- D; 2 – C; 3 –A; 4 -B

1. Define velocity?
Velocity is the rate of change of displacement. It is the displacement in unit time.

2. Distinguish distance and displacement?

 Distance Displacement i) The actual length of the path travelled by a moving body irrespective of the direction. i) The change in position of a moving body in a particular direction. ii) It is a scalar quantity. ii) It is vector quantity.

3. What do you mean by uniform motion?
An object is said to be in uniform motion if it covers equal distance in equal intervals of time how so ever bit or small these time intervals may be. A particle is in uniform motion when it moves with constant velocity.

4. Compare speed and velocity?

 Speed Velocity i) The rate of change of distance (or) the distance travelled in unit time. i) The rate of change of displacement in unit time. ii) It is a scalar quantity ii) It is vector quantity.

5. What do you understand about negative acceleration?
i) If final velocity is less than initial velocity, the velocity decreases with time and the value of acceleration is negative. It is called negative acceleration.
ii) Negative acceleration is called retardation (or) deceleration.

6. What remains constant in uniform circular motion? And what changes is continuously in uniform circular motion?
i) Object is moving with a constant speed along a circular path.
ii) The direction changes continuously in uniform circular motion.

7. Is the uniform circular motion accelerated? Give reasons for your answer?
Yes, the uniform circular motion is accelerated.
A body is said to be accelerated if the velocity of the body changes either in magnitude (or) in direction. But in the case, the change in velocity is only due to the change in direction.

8. What is meant by uniform circular motion? Give two examples of uniform circular motion.
When an object moves with constant speed along a circular path, the motion is called uniform circular motion.
Examples:
1) Revolution of earth around the sun.
2) Revolution of moon around the earth.
3) In an atom, an electron moves around the nucleus in a circular path.