Selina Textbook Solutions: Motion | Physics Class 7 ICSE PDF Download

 Page 1


Motion 
Points to Remember 
?  Motion— Motion is the change in position with respect to a set of stationary 
landmarks. 
?  Types of motion are translatory, rotatory and oscillatory. 
?  A body is said to move in a translatory motion if the whole body moves through 
the same distance in the same interval of time. 
?  A body is said to be in rotatory motion if it moves about a fixed point without 
changing the radius of its motion. 
?  A body is said to be in oscillatory motion if it moves to and fro about its mean 
position. 
?  A body is said to be in vibratory motion if the body moves to and fro in a particular 
style. 
?  Oscillation of pendulum is one complete to and fro motion. 
?  The maximum displacement on either side of a mean position is called amplitude. 
?  A motion which repeats itself at regular intervals of time is called periodic motion. 
?  A physical quantity which has only magnitude and no direction is called a scalar 
quantity. 
?  A physical quantity which has magnitude as well as direction is called a vector 
quantity. 
?  Speed is the distance travelled per unit time. It is a scalar quantity. 
?  The displacement per unit time is known as the velocity of the body. It is a vector 
quantity. 
?  The rate of change of velocity is called acceleration. It is a vector quantity. 
?  Frequency is the number of complete oscillations in one second. 
?  Unit of frequency is Hertz. 
?  Motion is of two types (a) uniform (b) non-uniform motion. 
Test yourself 
A. Objective Questions 
1. Write true or false for each statement 
(a) Two trains going in opposite directions with the same speed are at rest relative to 
each other. 
Answer. False. 
(b) A ball is thrown vertically upwards. Its motion is uniform throughout. 
Answer. False. 
Page 2


Motion 
Points to Remember 
?  Motion— Motion is the change in position with respect to a set of stationary 
landmarks. 
?  Types of motion are translatory, rotatory and oscillatory. 
?  A body is said to move in a translatory motion if the whole body moves through 
the same distance in the same interval of time. 
?  A body is said to be in rotatory motion if it moves about a fixed point without 
changing the radius of its motion. 
?  A body is said to be in oscillatory motion if it moves to and fro about its mean 
position. 
?  A body is said to be in vibratory motion if the body moves to and fro in a particular 
style. 
?  Oscillation of pendulum is one complete to and fro motion. 
?  The maximum displacement on either side of a mean position is called amplitude. 
?  A motion which repeats itself at regular intervals of time is called periodic motion. 
?  A physical quantity which has only magnitude and no direction is called a scalar 
quantity. 
?  A physical quantity which has magnitude as well as direction is called a vector 
quantity. 
?  Speed is the distance travelled per unit time. It is a scalar quantity. 
?  The displacement per unit time is known as the velocity of the body. It is a vector 
quantity. 
?  The rate of change of velocity is called acceleration. It is a vector quantity. 
?  Frequency is the number of complete oscillations in one second. 
?  Unit of frequency is Hertz. 
?  Motion is of two types (a) uniform (b) non-uniform motion. 
Test yourself 
A. Objective Questions 
1. Write true or false for each statement 
(a) Two trains going in opposite directions with the same speed are at rest relative to 
each other. 
Answer. False. 
(b) A ball is thrown vertically upwards. Its motion is uniform throughout. 
Answer. False. 
(c) The motion of a train starting from one station and reaching at another station is 
non-uniform. 
Answer. True. 
(d) A motion which repeats itself after a fixed interval of time is called periodic motion. 
Answer. True. 
(e) A ball thrown by a boy from a roof-top has oscillatory motion. 
Answer. False. 
(f) Mass has both magnitude and direction. 
Answer. False. 
(g) .Weight always acts vertically downwards. 
Answer. True 
(h) Mass varies from place to place but weight does not. 
Answer. False 
2. Fill in the blanks 
(a) Two boys cycling on the road with the same speed are at rest relative to each other. 
(b) The motion in a straight line is rectilinear motion. 
(c) One to and fro motion of a clock pendulum takes time = 2 s 
(d) 36 km h
-1
 = 10 m s
-1
 
(e) Total distance travelled = average speed × total time taken. 
(f) The weight of a girl is 36 kgf. Her mass will be 36 kg. 
(g) The weight of a body is measured using a spring balance. 
Activity 
Page 3


Motion 
Points to Remember 
?  Motion— Motion is the change in position with respect to a set of stationary 
landmarks. 
?  Types of motion are translatory, rotatory and oscillatory. 
?  A body is said to move in a translatory motion if the whole body moves through 
the same distance in the same interval of time. 
?  A body is said to be in rotatory motion if it moves about a fixed point without 
changing the radius of its motion. 
?  A body is said to be in oscillatory motion if it moves to and fro about its mean 
position. 
?  A body is said to be in vibratory motion if the body moves to and fro in a particular 
style. 
?  Oscillation of pendulum is one complete to and fro motion. 
?  The maximum displacement on either side of a mean position is called amplitude. 
?  A motion which repeats itself at regular intervals of time is called periodic motion. 
?  A physical quantity which has only magnitude and no direction is called a scalar 
quantity. 
?  A physical quantity which has magnitude as well as direction is called a vector 
quantity. 
?  Speed is the distance travelled per unit time. It is a scalar quantity. 
?  The displacement per unit time is known as the velocity of the body. It is a vector 
quantity. 
?  The rate of change of velocity is called acceleration. It is a vector quantity. 
?  Frequency is the number of complete oscillations in one second. 
?  Unit of frequency is Hertz. 
?  Motion is of two types (a) uniform (b) non-uniform motion. 
Test yourself 
A. Objective Questions 
1. Write true or false for each statement 
(a) Two trains going in opposite directions with the same speed are at rest relative to 
each other. 
Answer. False. 
(b) A ball is thrown vertically upwards. Its motion is uniform throughout. 
Answer. False. 
(c) The motion of a train starting from one station and reaching at another station is 
non-uniform. 
Answer. True. 
(d) A motion which repeats itself after a fixed interval of time is called periodic motion. 
Answer. True. 
(e) A ball thrown by a boy from a roof-top has oscillatory motion. 
Answer. False. 
(f) Mass has both magnitude and direction. 
Answer. False. 
(g) .Weight always acts vertically downwards. 
Answer. True 
(h) Mass varies from place to place but weight does not. 
Answer. False 
2. Fill in the blanks 
(a) Two boys cycling on the road with the same speed are at rest relative to each other. 
(b) The motion in a straight line is rectilinear motion. 
(c) One to and fro motion of a clock pendulum takes time = 2 s 
(d) 36 km h
-1
 = 10 m s
-1
 
(e) Total distance travelled = average speed × total time taken. 
(f) The weight of a girl is 36 kgf. Her mass will be 36 kg. 
(g) The weight of a body is measured using a spring balance. 
Activity 
 
Page 4


Motion 
Points to Remember 
?  Motion— Motion is the change in position with respect to a set of stationary 
landmarks. 
?  Types of motion are translatory, rotatory and oscillatory. 
?  A body is said to move in a translatory motion if the whole body moves through 
the same distance in the same interval of time. 
?  A body is said to be in rotatory motion if it moves about a fixed point without 
changing the radius of its motion. 
?  A body is said to be in oscillatory motion if it moves to and fro about its mean 
position. 
?  A body is said to be in vibratory motion if the body moves to and fro in a particular 
style. 
?  Oscillation of pendulum is one complete to and fro motion. 
?  The maximum displacement on either side of a mean position is called amplitude. 
?  A motion which repeats itself at regular intervals of time is called periodic motion. 
?  A physical quantity which has only magnitude and no direction is called a scalar 
quantity. 
?  A physical quantity which has magnitude as well as direction is called a vector 
quantity. 
?  Speed is the distance travelled per unit time. It is a scalar quantity. 
?  The displacement per unit time is known as the velocity of the body. It is a vector 
quantity. 
?  The rate of change of velocity is called acceleration. It is a vector quantity. 
?  Frequency is the number of complete oscillations in one second. 
?  Unit of frequency is Hertz. 
?  Motion is of two types (a) uniform (b) non-uniform motion. 
Test yourself 
A. Objective Questions 
1. Write true or false for each statement 
(a) Two trains going in opposite directions with the same speed are at rest relative to 
each other. 
Answer. False. 
(b) A ball is thrown vertically upwards. Its motion is uniform throughout. 
Answer. False. 
(c) The motion of a train starting from one station and reaching at another station is 
non-uniform. 
Answer. True. 
(d) A motion which repeats itself after a fixed interval of time is called periodic motion. 
Answer. True. 
(e) A ball thrown by a boy from a roof-top has oscillatory motion. 
Answer. False. 
(f) Mass has both magnitude and direction. 
Answer. False. 
(g) .Weight always acts vertically downwards. 
Answer. True 
(h) Mass varies from place to place but weight does not. 
Answer. False 
2. Fill in the blanks 
(a) Two boys cycling on the road with the same speed are at rest relative to each other. 
(b) The motion in a straight line is rectilinear motion. 
(c) One to and fro motion of a clock pendulum takes time = 2 s 
(d) 36 km h
-1
 = 10 m s
-1
 
(e) Total distance travelled = average speed × total time taken. 
(f) The weight of a girl is 36 kgf. Her mass will be 36 kg. 
(g) The weight of a body is measured using a spring balance. 
Activity 
 
 
 
3. Match the following 
 
Page 5


Motion 
Points to Remember 
?  Motion— Motion is the change in position with respect to a set of stationary 
landmarks. 
?  Types of motion are translatory, rotatory and oscillatory. 
?  A body is said to move in a translatory motion if the whole body moves through 
the same distance in the same interval of time. 
?  A body is said to be in rotatory motion if it moves about a fixed point without 
changing the radius of its motion. 
?  A body is said to be in oscillatory motion if it moves to and fro about its mean 
position. 
?  A body is said to be in vibratory motion if the body moves to and fro in a particular 
style. 
?  Oscillation of pendulum is one complete to and fro motion. 
?  The maximum displacement on either side of a mean position is called amplitude. 
?  A motion which repeats itself at regular intervals of time is called periodic motion. 
?  A physical quantity which has only magnitude and no direction is called a scalar 
quantity. 
?  A physical quantity which has magnitude as well as direction is called a vector 
quantity. 
?  Speed is the distance travelled per unit time. It is a scalar quantity. 
?  The displacement per unit time is known as the velocity of the body. It is a vector 
quantity. 
?  The rate of change of velocity is called acceleration. It is a vector quantity. 
?  Frequency is the number of complete oscillations in one second. 
?  Unit of frequency is Hertz. 
?  Motion is of two types (a) uniform (b) non-uniform motion. 
Test yourself 
A. Objective Questions 
1. Write true or false for each statement 
(a) Two trains going in opposite directions with the same speed are at rest relative to 
each other. 
Answer. False. 
(b) A ball is thrown vertically upwards. Its motion is uniform throughout. 
Answer. False. 
(c) The motion of a train starting from one station and reaching at another station is 
non-uniform. 
Answer. True. 
(d) A motion which repeats itself after a fixed interval of time is called periodic motion. 
Answer. True. 
(e) A ball thrown by a boy from a roof-top has oscillatory motion. 
Answer. False. 
(f) Mass has both magnitude and direction. 
Answer. False. 
(g) .Weight always acts vertically downwards. 
Answer. True 
(h) Mass varies from place to place but weight does not. 
Answer. False 
2. Fill in the blanks 
(a) Two boys cycling on the road with the same speed are at rest relative to each other. 
(b) The motion in a straight line is rectilinear motion. 
(c) One to and fro motion of a clock pendulum takes time = 2 s 
(d) 36 km h
-1
 = 10 m s
-1
 
(e) Total distance travelled = average speed × total time taken. 
(f) The weight of a girl is 36 kgf. Her mass will be 36 kg. 
(g) The weight of a body is measured using a spring balance. 
Activity 
 
 
 
3. Match the following 
 
 
4. Select the correct alternative 
(a) A book lying on a table is an example of 
1.  a body at rest 
2.  a body in motion 
3.  a body neither at rest nor in motion 
4.  none of these 
(b) The motion of a pendulum is 
1.  rotatory 
2. oscillatory 
3.  curvilinear 
4.  rectilinear 
(c) A car moving on a straight road is an example of 
1.  rotatory motion 
2.  rectilinear motion 
3.  oscillatory motion 
4.  periodic motion 
(d) A ball falls down vertically. Its motion is 
1.  periodic 
2.  linear 
3.  circular 
4.  vibratory 
(e) If a body covers equal distance in equal interval of time, the motion is said to be 
1.  uniform