I. OBJECTIVE TYPE QUESTIONS
A. Choose the correct answer.
1. A non-standard unit to measure length is
(a) centimetre (b) millimetre
(c) decimetre (d) cubit
Ans. (d) cubit
2. The girth of a tree can be measured using a
(a) metre scale (b) hand span
(c) string (d) measuring tape
Ans. (d) measuring tape
3. The movement of the earth around the sun is an example of
(a) rolling motion (b) periodic motion
(c) rectilinear motion (d) rotatory motion
Ans. (b) periodic motion
4. An object is said to be in motion if its position
(a) changes with time
(b) does not change with time
(c) changes for a particular time
(d) remains same from all reference points
Ans. (a) changes with time
5. Which of the following is a combination of rectilinear and rotational motion ?
(a) spin ball in cricket
(b) a hard kicked football
(c) heart-beat of a healthy person
(d) curvilinear motion of a car
Ans. (a) spin ball in cricket
6. In which of the following there is no change in the direction of movement of the body ?
(a) ) rotational motion (b) rectilinear motion
(c) curvilinear motion (d) periodic motion
Ans. (b) rectilinear motion
7. Which of the following is not periodic ?
(a) revolution of the earth around the sun
(b) movement of a pendulum
(a) beating of a drum
(b)
Ans. (c) beating of a drum
8. Which option correctly matches the given columns ?
(a) A.–(iv), B.–(iii), C.–(i), D.–(ii)
(b) A.–(iii), B.–(iv), C.–(ii), D.–(i)
(c) A.–(ii), B.–(iv), C.–(iii), D.–(i)
(d) A.–(iv), B.–(i), C.–(ii), D.–(iii)
Ans. (a) A.–(iv), B.–(iii), C.–(i), D.–(ii)
B. Fill in the blanks.
1. A is used for measuring the waistline of a person.
2. The SI unit of length is .
3. The length of a curved line can be measured by using a .
4. A plucked string of a sitar executes motion.
5. A body undergoing both translatory and rotatory motions is said to be .
Ans. 1. Measuring tape 2. Metre
3. Thread and scale 4. Vibratory
5. Rolling
C. State True or False. Also correct the false statements.
1. Each measurement consists of a number and a unit.
2. The SI unit of distance is kilometre.
3. The objects which do not change their position with time are said to be at rest.
4. Motion of a fl is an example of curvilinear
motion.
5. The motion of a spinning top is rotational motion.
Ans. 1. True 2. False 3. True 4. False 5. True
D. 
Tick (4) the odd-one out giving reason.
1. Aeroplane, Bus, Railway train, Ship, Bullock cart
2. Metre, Kilometre, Yard, Centimetre
3. Handspan, Palm, Foot, Cubit
4. Motion of a stone dropped from certain height,
Motion of a fly,
Motion of a bullet fired from a gun (up to short
distance), Motion of a car on a straight road
5. Motion of the moon around the earth, Motion of the earth around the sun,
Motion of a merry-go-round, Heart-beat in a
healthy person
Ans. 1. Bullock cart
2. Yard
3. Foot
4. Motion of a fly
5. Motion of a merry-go-round
A. Assertion-Reason
For question numbers 1 to 5, two statements are given— one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below :
(a) Both Assertion and Reason are true and Reason is the correct explanation of the Assertion.
(b) Both Assertion and Reason are true but Reason is not correct explanation of the Assertion.
(c) Assertion is true but Reason is false.
(d) Assertion is false but Reason is true.
1. Assertion (A) : Breathing is also an example of motion.
Reason (R) : When we breathe, there is a flow of air that goes in and out of our lungs.
2. Assertion (A) : Motion is linear when all the parts of an object move from one place to another at a particular time.
Reason (R) : An object moving along a circular path has linear motion.
3. Assertion (A) : Oscillatory motion is a type of motion in which an object moves around its mean position.
Reason (R) : The motion of a pendulum of a wall clock is an example of oscillatory motion.
4. Assertion (A) : Hand span, foot, cubit can be used as the unit of length.
Reason (R) : Body parts used for measuring length have the same value for each person.
5. Assertion (A) : Metre is the standard unit of length.
Reason (R) : Multiples and submultiples of metre can also be used to measure length.
Ans. 1. (a) 2. (c) 3. (a) 4. (c) 5. (b)
1. Why a hand span cannot be used universally as a unit of length ?
Ans. Hand span cannot be used as standard units of length because the size of hand span varies from person to person. So, two different people may give different measurements for the same length, which is not desirable for a standard unit.
2. What is meant by rest and motion ?
Ans. An object that does not change its positions with time with respect to a fixed point is said to be at rest. An object that changes its positions with time with respect to a fixed point is said to be in motion.
3. Differentiate between the motion of a ceiling fan and that of sewing machine.
Ans.
Motion of a ceiling fan | Motion of a sewing machine |
The motion of the ceiling fan is the circular motion. | The motion of the sewing machine is the rotational motion. |
Fan blades move in a periodic pattern. | The needle of the sewing machine has a periodic motion. |
4. The distance between Rohit’s house and Richa’s house is 20,000 m. Express it in km.
Ans. Since 1000 m = 1 km Or 1m = 1/1000 km
Therefore 20,000 m = 20,000/1000 = 20 km
5. Arrange the following in decreasing order : 1 mm, 1 km, 1 cm, 1 dm, 1 m
Ans. Since 1 m = 100 cm, 1 dm= 10 cm and 1 cm = 10 mm
∴ 1 m = 100 × 10 = 1000 mm
Now, 1 km = 1000 m
∴ 1 km = (1000 × 100) cm = 100000 cm =
(100000 × 10) mm
= 1000000 mm
1 km> 1m>1dm> 1cm>1mm
6. Name the three types of translatory motion. Give one example of each type.
Ans. Three types of translatory motion are:
• Linear motion (or rectilinear motion): The motion of cars on a straight road
• Curvilinear motion (or Circular motion): The motion of a car along a curved road
• Random motion: Motion of a football or hockey player on the ground.
III. LONG ANSWER TYPE QUESTIONS
1. Why do we need standard units for measurements?
Ans. We need standard unit for measurement for precision and accuracy. For proper dealing, measurement should be same for everybody at all places. Thus there should be uniformity in measurement. For the sake of uniformity we need a common set of units of measurement, which are called standard units.
2. Mention the precautions to be observed while measuring the length of a pencil using a ruler.
Ans. To measure length of an object accurately, following precautions should be taken:
• The scale should be placed along the length to be measured. The scale should be placed very close to the object to be measured.
• Keep your eye in line with the point of measurement. If the eye is not in line with the point of measurement, the measured length will be either shorter or longer than the actual length.
Do not start measurement from the worn out or damaged end of the scale. If the zero end of the scale is damaged, start measurement from some other mark of the scale.
3. Name the types of motion executed by a rolling body. Give one example of rolling motion.
Ans. A rolling body executes both translational and rotational motion i.e. it moves along its axis and also moves linearly
The motion of a cylinder on an inclined plane or that of a bicycle wheel are examples of rolling motion.
4. What is circular motion ? How does it differ from rotatory motion ?
Ans.
Rotatory motion | Circular motion |
A body is said to be in rotatory motion if it moves about a fixed axis. | The motion of a body along a circular path is called circular motion. |
The axis of rotation passes from a point in the body itself. | The axis of revolution doesn’t pass through the body. |
The body undergoes rotation. | The body undergoes revolution |
Ex.- Motion of earth about its own axis is an example of rotatory motion | Ex.- Motion of earth around the sun is an example of circular motion. |
5. What kind of motion is executed by
(a) an ant
(b) a car moving on the straight road
(c) pendulum of a clock
(d) potter’s wheel
(e) a stone tied to a string
(f) ) a spin ball
Ans. (a) Random motion
(b) Translatory motion
(c) Periodic motion
(d) Rotational motion
(e) Circular motion
(f) Rotational motion
6. State three precautions to be taken to measure the length of an object using a metre scale.
Ans. To measure length of an object accurately, following precautions should be taken:
• The scale should be placed along the length to be measured. The scale should be placed very close to the object to be measured.
• Keep your eye in line with the point of measurement. If the eye is not in line with the point of measurement, the measured length will be either shorter or longer than the actual length.
Do not start measurement from the worn out or damaged end of the scale. If the zero end of the scale is damaged, start measurement from some other mark of the scale.
IV. HIGHER ORDER THINKING SKILLS
1. Why are the co-passengers in a train appear to be stationary, while the trees outside appear to move to a passenger sitting in the train ?
Ans. The trees appear to be in moving opposite direction while travelling in a train because the position of trees is changing with respect to us. Whereas, our co-passenger in a train seem to be at stationary position because their position is not changing with respect to us.
2. A turning screw undergoes two kinds of motion at the same time. Identify the two kinds of motion.
Ans. Turning screw undergoes a circular motion and a linear motion in forward direction along with it.
3. A student has to measure the length of his pencil. The zero mark on the scale is not clearly visible. How should he/she use the scale to get the correct length of the pencil ?
Ans. The student can measure the length from the 1cm mark in the scale and add 1cm later to his measurement. This will give him the correct length of the pencil.
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