Written as per the revised syllabus prescribed for the academic year 2017-2018, by the Maharashtra State Bureau of Textbook Production and Curriculum Research, Pune.
STD. IX Science and Technology Salient Features •
Written as per the new textbook.
•
Exhaustive coverage of entire syllabus through summative and formative section.
•
Ample numericals for thorough revision.
•
Memory maps provided for revision at a glance.
• Chapter-wise assessment with every chapter for knowledge testing.
Printed at: Repro India Ltd., Navi Mumbai © Target Publications Pvt. Ltd. No part of this book may be reproduced or transmitted in any form or by any means, C.D. ROM/Audio Video Cassettes or electronic, mechanical including photocopying; recording or by any information storage and retrieval system without permission in writing from the Publisher. P.O. No. 65044
10054_11870_JUP
Contents No.
Topic Name
Page No.
1.
Laws of Motion
1
2.
Work and Energy
23
3.
Current Electricity
42
4.
Measurement of Matter
56
5.
Acids, Bases and Salts
76
6.
Classification of Plants
97
7.
Energy Flow in an Ecosystem
106
8.
Useful and Harmful Microbes
116
9.
Environmental Management
125
10.
Information Communication Technology (ICT)
139
11.
Reflection of Light
147
12.
Study of Sound
161
13.
Carbon : An Important Element
174
14.
Substances in Common Use
189
15.
Life Processes in Living Organisms
207
16.
Heredity and Variation
224
17.
Introduction to Biotechnology
237
18.
Observing Space : Telescopes
252
Note: Textual exercise questions are respresented by * mark.
1
Laws of Motion Summative Assessment
Objective Section Fill in the blanks 1.
The shortest distance between initial and final points of movement of the body is called _______ of the body.
2.
The magnitude of velocity and _______ will be equal if motion is along a straight path.
3.
Retardation means _______ acceleration.
4.
If velocity of an object changes by unequal amounts in equal time intervals, the object is said to be in _______ acceleration.
5.
Slope of distance-time graph gives _______ in case of uniform motion.
6.
The variation of velocity and time of a train in motion can be represented by _______ graph.
7.
The first kinematical equation gives relation between _______ and time.
8.
When a body is performing uniform _______ motion, its velocity changes at every point.
9.
The direction of velocity of an object performing uniform circular motion is along the _______ direction to its position.
10.
While sharpening a knife, sparks fly off _______ from the grinding stone.
11.
_______ is a quantitative measure of inertia of body.
12.
A person gets a forward jerk when a car stops suddenly due to _______.
13.
An _______ force acting on an object brings it in motion.
14.
A force of 400 N is applied to a table of mass 80 kg, hence the acceleration produced is _______.
15.
The momentum of a body of mass 5 kg is 10 kg m/s, then its velocity will be _______.
16.
Law of conservation of momentum is a corollary to Newton’s _______ of motion.
17. In a collision, _______ is always conserved. Answers: 1. displacement 2. speed 3. negative 4. non-uniform 5. velocity 6. velocity-time 7. velocity 8. circular 9. tangential 10. tangentially 11. Mass 12. inertia 13. unbalanced 14. 5 m/s2 15. 2 m/s 16. third law 17. total momentum
Right or Wrong. If wrong, write the correct sentence 1.
Whenever the displacement of an object is zero, distance traversed by it is also zero. Ans: False. Even if the displacement of an object is zero, the actual distance traversed by it may not be zero. 2.
Earth moves around the sun with uniform velocity. Ans: False. Earth moves around the sun with uniform speed. 3. Acceleration is always positive. Ans: False. Acceleration can be positive, negative or zero. 4.
An accelerated motion is an example of non-uniform motion. Ans: True. 5.
For non-uniformly accelerated motions, velocity-time graph is a straight line. Ans: False. For uniformly accelerated motions, velocity-time graph is a straight line.
6. Circular motion is an accelerated motion. Ans: True. 7.
Inertia is inability of an object to change its state of motion on its own. Ans: True. 8.
When a body is at rest, there is no force acting on it. Ans: False. When a body is at rest there is balanced force acting on it.
1
Std. IX: Science and Technology 9.
Force is a reciprocal action between two objects. Ans: True. 10.
Momentum is necessary to cause a change in force applied on an object. Ans: False. Force (unbalanced) is necessary to cause change in momentum associated with an object. 11.
When net force F acts for time t on an object, change in momentum produced in it is equal to Ft. Ans: True. 12.
When no external force is acting on the objects, momentum gets redistributed between objects during collision. Ans: True.
Odd one out
Subjective Section Define 1. Motion Ans: The change in the position of an object with respect to its surroundings is called motion. 2. Distance Ans: The actual path followed by a body between the initial and final points of motion (movement) is called distance. 3. Displacement Ans: The shortest distance between the initial and final points of movement is called displacement. 4. Speed Ans: The distance covered by a body in unit time is called speed.
1. Force, Momentum, Acceleration, Mass. Ans: Mass: It is a scalar quantity whereas remaining are vector quantities.
5. Velocity Ans: The distance travelled by a body in a given direction in unit time is called velocity.
2. newton, joule, kg m/s2, dyne Ans: joule: It is a unit of energy whereas remaining are units of force.
6. Uniform motion Ans: The motion in which the object covers equal distances in equal intervals of time is called uniform motion.
3.
Motion of vehicles on a crowded street, A man going for a stroll on a beach, soldiers marching, motion of fishes in water. Ans: Soldiers marching: This is an example of uniform motion whereas the rest are examples of non uniform motion.
Match the following *1.
Match the first column with appropriate entries in the second and third columns and remake the table.
Column 1 Column 2 Column 3 i. Negative a. The velocity p. A car, initially acceleration of the object at rest reaches remains a velocity of constant 50 km/hr in 10 seconds ii. Positive b. The velocity q. A vehicle is acceleration of the object moving with decreases a velocity of 25 m/s iii. Zero c. The velocity r. A vehicle acceleration of the object moving with increases the velocity of 10 m/s, stops after 5 seconds. Ans: (i b, r); (ii c, p); (iii a, q)
22
7. Non uniform motion Ans: The motion in which an object covers unequal distances in equal intervals of time is called non uniform motion. 8. Acceleration Ans: The rate of change of velocity is called acceleration. 9. Uniform circular motion Ans: When an object moves with constant speed along a circular path, the motion is called uniform circular motion. 10. Kinematic equations Ans: A set of three equations which analyses rectilinear motion of uniformly accelerated body and helps to predict the position of body are called as kinematic equations. 11. Inertia Ans: The tendency of a body to resist change in a state of rest or state of motion is called inertia. 12. Momentum Ans: Momentum is the product of mass and velocity of an object. 13. 1 newton Ans: The force which causes to move a body of mass 1 kg with an acceleration of 1 m/s2 is called 1 newton force.
Chapter 1: Laws of Motion 14. 1 dyne Ans: The force which causes to move a body of mass 1 g with an acceleration of 1 cm/s2 is called 1 dyne force.
State the following law
iii.
3.
1. Newton’s first law of motion Ans: An object continues to remain at rest or in a state of uniform motion along a straight line unless an external unbalanced force acts on it.
5.00 5.30 6.00 6.30 7.00 7.30 8.00
3. Newton’s third law of motion Ans: Every action force has an equal and opposite reaction force which acts simultaneously. 4. Law of conservation of momentum Ans: When no external force acts on two interacting objects, their total momentum remains constant. It does not change. OR When two objects collide, the total momentum before collision is equal to the total momentum after collision.
i. ii. iii.
Answer the following How can the velocity of an object be changed? Ans: Velocity depends on speed and direction. It can be changed by i. changing speed, ii. changing direction of motion. iii. changing speed as well as direction of motion.
Use your brain power! (Textbook page no. 4) Amar, Akbar and Anthony are travelling in different cars with different velocities. The distances covered by them during different time intervals are given in the following table. Time in the clock
2. Newton’s second law of motion Ans: The rate of change of momentum is proportional to the applied force and the change of momentum occurs in the direction of the force.
iv.
1.
Give one example of each of the following: i. change in speed without a change in direction of motion of a body. ii. change in direction of motion without a change in speed of a body. iii. change in speed as well as direction of motion of a body. Ans: i. When a body falls under gravity (free fall), its speed increases, but its direction of motion remains the same. ii. When a body moves along a circular path, covering equal distances in equal intervals of time, its direction of motion changes continuously but there is no change in its speed.
Ans: i. ii. iii.
iv.
2.
When a body is projected obliquely in air, it moves along a curved path such that its speed as well as direction of motion change continuously.
Distance covered by Amar in km 0 20 40 60 80 100 120
Distance covered by Akbar in km 0 18 36 42 70 95 120
Distance covered by Anthony in km 0 14 28 42 56 70 84
What is the time interval between the notings of distances made by Amar, Akbar and Anthony? Who has covered equal distances in equal time intervals? Are all the distances covered by Akbar in the fixed time intervals the same? Considering the distances covered by Amar, Akbar and Anthony in fixed time intervals, what can you say about their speeds? 30 minutes. Amar and Anthony have covered equal distances in equal time intervals. No. Akbar has covered unequal distances in equal time intervals. Amar and Anthony are travelling with uniform speed while Akbar is travelling with non-uniform speed.
4.
Use your brain power! (Textbook page no. 5) i. When an object is at rest in the beginning of its motion, what is its initial velocity? ii. When an object comes to rest at the end of its motion, what is its final velocity? Ans: i. When an object is at rest in the beginning of its motion, its initial velocity is zero. ii. When an object comes to rest at the end of its motion, its final velocity is zero.
3
Std. IX: Science and Technology 5.
Use your brain power! (Textbook page no. 6) What difference do you see in the distancetime graphs for uniform and non-uniform motion? Ans: i. In uniform motion, an object covers equal distances in equal time intervals. Hence, for such a motion, graph of distance-time shows a direct proportionality between distance and time and thus, is a straight line. ii. In non-uniform motion, an object covers unequal distances in equal time intervals. Hence, for such a motion, graph of distance-time does not show a direct proportionality between distance and time and can have any shape depending on how distance varies with time. Explain with example: i. Positive acceleration ii. Negative acceleration iii. Zero acceleration Ans: i. Positive acceleration: When the velocity of a body increases with time, its acceleration is positive. Here acceleration is in the direction of velocity. Eg.: A ball rolling down an inclined plane. ii. Negative acceleration: When the velocity of a body decreases with time, its acceleration is negative. Here acceleration is opposite to direction of velocity. Eg.: A ball moving up an inclined plane. iii. Zero acceleration: When there is no change in the velocity of a body with time (i.e., the velocity is uniform), its acceleration is zero. Eg.: When body is at rest, its acceleration is zero.
i.
a=
In the case of a body moving along a straight line with uniform acceleration, obtain the kinematical equations of motion by graphical method. Ans: Kinematical equations of motion by graphical method:
Acceleration (a) =
ii.
u
C
Equation for position-time relation: Let distance covered by the object be ‘s’ in the time interval ‘t’ under uniform acceleration ‘a’. From figure, the distance travelled is given by area enclosed within EABD. s = area of quadrilateral EABD s = area of rectangle ACDE + area of ACB 1 AC BC 2
But EA = u, DE = AC = t, BC = at
1 t at 2 1 s = ut + at2 2
s = ut +
….(2)
Equation (2) is the second kinematical equation and represents position-time relation. iii.
Position-velocity relation: The distance ‘s’ travelled by object in time ‘t’ under uniform acceleration ‘a’ is given by area within EABD. s = Area of trapezium EABD
s=
B A
BC t
BC = at To find change in velocity, draw AC parallel to OD. BD = BC + CD = BC + AE But BD = v, AE = u, BC = at BD = BC + AE v = at + u v = u + at ….(1) Equation (1) is the first kinematical equation and represents velocity-time relation.
s = (ED EA) +
velocity v
change in velocity time
From figure,
6.
7.
Equation for velocity-time relation: Consider an object having non-zero initial velocity ‘u’, starting from point A. Its velocity goes on increasing with respect to time and becomes ‘v’ when it reaches point B as shown in the figure. The change in velocity is at uniform rate. Acceleration of the body is given by,
1 (BD + EA) ED 2
But EA = u, BD = v and ED = t O
44
E
D
time
s=
1 (v + u) t 2
….(3)
Chapter 1: Laws of Motion
From equation (1),
vu a= t vu t= a
….(4)
From equation (3) and (4),
v u 1 (v + u) 2 a 2 2 v u s= 2a s=
2as = v2 u2 ….(5) v2 = u2 + 2as Equation (5) is the third kinematical equation and represents positionvelocity relation.
8. What is uniform circular motion? Ans: i. When an object moves in a circular path with uniform speed, its motion is uniform circular motion. ii. Magnitude of velocity i.e., speed of a particle performing uniform circular motion is given by v=
circumference of the circle timefor one revolution of the particle
v=
2r t
iii.
where ‘r’ is the radius of the circle. Example: Motion of tip of second hand of clock.
11. Write a note on: Momentum Ans: i. Momentum (p) is product of mass (m) and velocity (v) of an object i.e., p = mv ii. It is a vector quantity with SI unit kg m/s and CGS unit g cm/s. iii. Its direction is same as that of velocity of the object. iv. When an unbalanced force applied on an object brings changes in its velocity, momentum of the object also changes. Thus, unbalanced force is necessary to cause changes in momentum. 12.
Derive the equation of force using Newton’s second law of motion. Ans: i. Let a body of mass m, moving with velocity u be subjected to force F acting in the direction of motion. Suppose v is the velocity of the body after time t. ii. Total initial momentum of the body = mu and total final momentum of the body = mv iii. Change in momentum = Final momentum initial momentum = mv mu Rate of change of momentum Change in momentum time mv mu = t m(v u) = t vu = a = acceleration But t
=
9.
Intext Question. (Textbook page no. 9) Can you give more examples of uniform circular motion? Ans: Examples of uniform circular motion: i. Motion of the earth around the sun. ii. Motion of the moon around the earth. iii. Motion of the electron around the nucleus. iv. Motion of blades of a fan. v. Motion of a communication satellite (a geostationary satellite used for communication) around the earth. The forces of 15 N and 10 N are acting on a stone from north and south direction respectively. i. Discuss, whether these forces are balanced or unbalanced. ii. What is the effect of resulting force? Ans: i. As the magnitude of two forces are unequal and direction of application are opposite i.e., one along the north and other along the south, the two forces of 15 N and 10 N are unbalanced forces. ii. Resulting force F = F1 + ( F2) …[since direction is opposite]
F = 15 10 = 5 N This resulting force of magnitude 5 N moves the stone towards north direction.
iv. v.
10.
13.
Rate of change of momentum = ma According to Newton’s second law of motion, Rate of change of momentum Force ma F F = kma, where k is a constant If F = 1 N, m = 1 kg, a = 1 m/s2 then, k=1 F = ma Force = mass acceleration
For a body of certain mass and certain velocity i. if mass is doubled and velocity is halved, is there any change in its momentum? ii. if velocity and mass both become double, what will be its resulting momentum?
5
Std. IX: Science and Technology iii. Ans: i. ii.
iii.
14.
if mass of a body is doubled, but velocity remains same, then what will be the resulting momentum? No, there is no change in momentum because mass and velocity both vary directly with momentum. If mass and velocity both become double then resulting momentum will be 2 2 times i.e., 4 times that of initial momentum. If mass of a body is doubled but velocity remains same then its new momentum will be 2 1 times i.e., 2 times that of initial momentum.
Use your brain power! (Textbook page no. 14) i. While hitting a ball with a bat, the speed of the bat decreases. ii. A gun recoils i.e., moves backwards when a bullet is fired. iii. Mechanism of firing of a rocket. How will you explain these with the help of Newton’s third law of motion? Ans: i. a. When a bat strikes a ball, the ball also exerts an equal and opposite force of reaction on the bat. b. The force acting on the ball projects it with high velocity, while the reaction force acting on the bat slows down its forward motion. Hence, the speed of the bat decreases. ii. a. When a bullet is fired from a gun, a force is exerted by the gun on the bullet. Bullet due to its less mass, gets accelerated largely and acquires high velocity. b. At the same time the bullet also exerts an equal and opposite force on the gun. The gun being comparatively massive moves in the opposite direction with small velocity. iii. a. The principle used for the motion of a rocket is based on Newton’s third law of motion. b. When the fuel in the rocket is ignited; it burns as a result of chemical reaction. c. The exhaust gases escape with force through a small opening at the tail end of rocket in downward direction. d. They exert an equal and opposite reaction force on the rocket. e. It is this reaction force which makes the rocket move in the forward direction.
66
15.
Explain the principle of conservation of momentum. Ans: i. According to principle of conservation of momentum, the total momentum before collision of both the bodies is equal to the total momentum after collision. ii. Consider two bodies A and B. Let mass of A = m1, Initial velocity of A = u1 Final velocity of A = v1 and force acting on A due to B = F1 Mass of B = m2, Initial velocity of B = u2 final velocity of B = v2 and Force acting on B due to A = F2 iii. When A and B collide, a force F1 due to body B acts on A and the body A accelerates. iv. According to Newton’s third law, body A also exerts an equal and opposite force on body B. v. Since these forces are opposite in direction, F2 = F1 m2a2 = m1a1
m2 v2 u 2 m1 v1 u1 = t t
m2 (v2 u2) = m1 (v1 u1) m2v2 m2u2 = m1v1 + m1u1 m1v1 + m2v2 = m1u1 + m2u2 Final momentum = Initial momentum. Hence, total momentum in a collision is always conserved. 16.
Give 2 examples of principle of conservation of linear momentum. Ans: Examples: i. When a person jumps from a boat, the boat is pushed away: When a person jumps from a small boat on the shore, he imparts an equal and opposite momentum to the boat. Therefore, the boat is pushed away backward. ii. A hammer rebounds when hitting a nail into a wall: When a nail is driven into a wall by striking it with a hammer, the hammer is seen to rebound after striking the nail. This is because the hammer imparts a certain amount of momentum to the nail and the nail imparts an equal and opposite amount of momentum on the hammer. *17. Take 5 examples from your surroundings and give explanation based on Newton’s laws of motion. Ans: Example 1: When we are travelling by a bus, we experience backward jerk as the bus starts
Chapter 1: Laws of Motion moving from rest. This is in accordance with Newton’s first law of motion. Explanation: i. A body resists change in its state of rest or of motion due to inertia. ii. When the bus is at rest, inside the bus we are also at rest. iii. As the bus starts moving, the portion of the our body which is in contact with the bus acquires velocity, but the upper part of the body tries to remain at rest. iv. As a result, we exert an inertia of rest and get a backward jerk, when the bus moves in the forward direction. Example 2: A carpet when lifted up and given jerks, dust falls out of it. This is in accordance with Newton’s first law of motion. Explanation: i. When we dust a carpet, by lifting it, the carpet is set into motion. ii. While the dust remains in its state of rest due to inertia of rest. iii. As a result, dust particles get separated from carpet, fall down under the effect of gravitational force and carpet becomes clean. Example 3: While catching a ball, cricketer moves his hands backwards. This is in accordance with Newton’s second law of motion. Explanation: i. In the act of catching the ball, by drawing hands backward, cricketer allows longer time for his hands to stop the ball. ii. By Newton’s second law of motion, force applied depends on the rate of change of momentum. iii. Taking longer time to stop the ball ensures smaller rate of change of momentum. iv. Due to this, the cricketer can stop the ball by applying smaller amount of force and thereby not hurting his hands. Example 4: A book kept on a table remains stationary. This is in accordance with Newton’s third law of motion. Explanation: i. A book kept on a table has some weight. This weight is the force acting on the table. ii. By Newton’s third law of motion, every action has an equal and opposite reaction. iii. Thus, the table also exerts an upward force on and balances weight of the book.
iv.
Thus, both the forces are balanced and there is no displacement. Hence, a book kept on a table remains stationary. Example 5: An air filled balloon held in hand when released, moves forward. This is in accordance with Newton’s third law of motion. Explanation: As air is released out in downward direction, it applies equal and opposite force on balloon pushing it forward. *18. Complete the sentences and explain them. i. The minimum distance between the start and finish points of the motion of an object is called the _______ of the object. ii. Deceleration is _______ acceleration iii. When an object is in uniform circular motion, its _______ changes at every point. iv. During collision _______ remains constant. v. The working of a rocket depends on Newton’s _______ law of motion. Ans: i. The minimum distance between the start and finish points of the motion of an object is called the displacement of the object. Explanation:
A
ii.
B
Consider a person cycling from point A to point B through hills as shown in the figure above. In the case, he covers distance 2a + 2b km but his displacement being minimum distance between points A and B equals to C km. Deceleration is negative acceleration. Explanation: When velocity of an object decreases with time, it is said to be decelerated motion and acceleration in such case is said to be deceleration. As final velocity of object is lesser than its initial velocity, i.e., v < u, from formula, acceleration, a =
iii.
C km
vu becomes negative. t
When an object is in uniform circular motion, its velocity changes at every point.
7
