Measurement of Length and Motion Class 6 Questions and Answers NCERT Solutions
Class 6 Science Chapter 5 Measurement of Length and Motion Question Answer
Intext Question:
(Page no. 83)
Question 1.
Would it be convenient to use the unit metre to measure larger lengths, such as the length of a railway track between two cities, or to measure smaller lengths, such as the thickness of a page of a book?
Answer:
Length and distance measurements are given in units and the number of units. For long distances if small units like meters are used the number of units will be very large. This becomes inconvenient. Therefore long distances like distances among two cities are measured in kilometres.
Small thicknesses or lengths like the thickness of a page of book are measured in very small units like mm. If this is measured in metres or km then number of units become very small fractions inconvenient to handle. Lengths like those of a room are measured in metres for convenience
(Page no. 89)
Question 1.
What do such kilometre stones indicate? How could Padma conclude that she was getting closer to her destination?
Answer:
Kilometre stones on the roads between cities and places indicate the distance left to reach a place or city (the reference point). Padma saw that earlier kilometre stone showed the distance to Delhi as 70 km and the next kilometre stone showed the distance to Delhi as 60 km. She concluded that she was in motion and moving towards Delhi (the reference point with respect to which she was changing her position with time).
Question 2.
Does this mean that the position of Padma, with respect to the reference point, is changing with time? When does the position of an object change with respect to a reference point? Does it change when an object is moving?
Answer:
- Padma saw from the kilometre stones that the distance to Delhi is decreasing with time. This means that with respect to Delhi (reference point here), she was changing position with time.
- When the position of an object changes with time with respect to a reference point the object is said to be in a state of motion or is moving.
- Padma was changing her position with time with respect to Delhi, means that she was moving closer and closer to Delhi with time.
Let Us Enhance Our Learning
Question 1.
Some lengths are given in column I of table. Some units are given in column II. Match the lengths with the units suitable’for measuring those lengths.
| Column I | Column II |
| 1. Distance between Delhi and Lucknow 2. Thickness of a coin. 3. Length of an eraser. 4. Length of school ground. |
(a) centimetre (b) kilometre (c) metre (d) milimetre |
Answer:
| Column I | Column II |
| 1. Distance between Delhi and Lucknow | (b) kilometre |
| 2. Thickness of a coin. | (d) millimetre |
| 3. Length of an eraser | (a) centimetre |
| 4. Length of school ground. | (c) metre |
Question 2.
Read the following statements and mark True (T) or False (F) against each.
(i) The motion of a car moving on a straight road is an example of linear motion.
(ii) Any object which is changing its position with respect to a reference point with time is said to be in motion.
(iii) 1km=100cm
Answer:
(i) True
(ii) True
(iii) False.
Question 3.
Which of the following is not a stand and unit of measuring length ?
(i) millimetre
(ii) centimetre
(iii) kilometre
(iv) handspan
Answer:
(iv) handspan.
Question 4.
Search for the different scales or measuring tapes at your home and school. Find out the smallest value that can be measured using each of these scales. Record your observations in a tabular form.
Answer:
| Scale | Smallest value that can be measured |
| 1. Metre scale or ruler 2. Measuring tape |
Millimetre (mm) Millimetre (mm) |
Question 5.
Suppose the distance between your school and home is 1.5 km. Express it in metres.
Answer:
1 km = 1000 m
So, 1.5 km = 1.5 x 1000
= 1500 metres.
Question 6.
Take a tumbler or a bottle. Measure the length of the curved part of the base of glass or bottle and record it.
Answer:
Hint: Use a flexible measuring tape or a piece of string to measure the length of the curved part of the base of the tumbler, then measure the string against a ruler.
Question 7.
Measure the height of your friend and express it in (i) metres, (ii) centimetres and (iii) milimetre.
Answer:
Height of the friend =1.65 m
(i) Height of the friend =1.65 m
(ii) 1 m =100 cm
1.65 m =100 × 1.6 cm
=165 cm
(iii) 1 m =1000 mm
1.65 m =1000 × 1.65 mm
= 1650mm
Question 8.
You are given a coin. Estimate how many coins are required to be placed one after the other length wise, without leaving any gap between them, to cover the whole length of the chosen side of a note book. Verify your estimate the same side of the notebook and the size of the coin using a 15 cm -scale.
Answer:
Length of 1 coin = 1mm
Length of the notebook =15 cm
=15 × 10
=150 mm
Required number of coins
= \(\frac{150 \mathrm{~mm}}{1 . \mathrm{mm}}\) =1.50
Question 9.
Give two examples each for linear, circular and oscillatory motions.
Answer:
Examples of linear motion :
(i) The motion of a car along a straight road.
(ii) The motion of a stone dropped from a certain height.
Examples of circular motion :
(i) The movement of moon around the earth.
(ii) The movement of earth around the sun.
Examples of oscillatory motion :
(i) Motion of the pendulum of a wall clock.
(ii) Motion of the heart muscles in a healthy person.
Question 10.
Object.different objects around you. It is easier to express the length of some objects in mm, some objects in cm and some in m. Make a three objects in each caterory and enter them in the table.
| Size | Object |
| mm | |
| cm | |
| m |
Answer:
| Size | Object |
| mm | (i) Thickness of a coil. |
| (ii) Thickness of a thin wire | |
| cm | (i) Length of a pencil. |
| (ii) Length of a note book | |
| m | (i) Length of a room |
| (ii) The height of a tree |
Question 11.
A roller coaster track is made in the shape shown in Fig. A ball starts from point A and escapes through point F. Identify the types of motion of the ball on the roller coaster and corresponding portions of the track.
Answer:
AB-track – Rectilinear motion.
BC-track – Rectilinear motion
CD-track – Circular motion
EF-track – Rectilinear motion.
Question 12.
Tasneem wants to make a metre scale by herself. She considers the following materials for it – plywood, paper, cloth, stretchable rubber and steel. Which of these should she not use and why ?
Answer:
She should not use plywood, paper, cloth stretchable rubber. The rulers made by these materials can bend. But a metre scale made of steel, cannot bend at all.
Question 13.
Thick design and develop a card game on conversion of units of length to play with your friends.
Answer:
Suppose we have red and yellow coloured cards. The red cards show layer distances such as 1 kilometre, 1 metre, 1 cm and mm. Similarly, yellow cards show smaller lengths such as 1000m, 10cm, 10m and 1000 mm . Arrange these cards to show conversion of units of length.
| Red card | Card yellow |
| 1. 1 km | (a) 1000 m |
| 2. 1 m | (b) 100 m |
| 3. 1 cm | (c) 10 mm |
| 4. 1 m | (d) 1000 mm |
Activities:
Activity 1.
Aim: To measure the given objects (comb, pen, a pencil, eraser).
Materials Required : A metre scale, comb, pen, pencil, eraser.
Procedure:
1. Measure the length of the given objects one by one using a metre scale.
| Name of the object | Length of the object |
| 1. Comb | ……………… cm |
| 2. Pen | ……………… cm |
| 3. Pencil | ……………… cm |
| 4. Eraser | ……………… cm |
Result :
1. The length of the given comb = ……………… cm
2. The length of the given pen =……………..
3. The length of the given pencil = ……………..cm
4. The length of the given eraser = …………….. cm
Precautions:
- The scale should be placed along the length to be measured.
- The eye should be exactly in front of the point where the measurement is to be taken.
Units of length, such as kilometre, metre, centimetre and mulimetre, begin with a lowercase letter, except at the beginning of a sentence. Their symbols km, m, m and mm are also written in lower case letters and never followed by ‘s’ for the plural. A full stop is not written after the symbol, except at the end of a sentence. While writing the length, always leave a space between the number and the unit.
Activity 2.
Aim: Observe things around up.
Materials Required: Cow, man, birds, a house, tree.
Procedure:
1. Look around and prepare a list of five objects that are in motion and five objects that are at rest.
Observations:
| Object in motion | Justification | Object at rest | Justification |
| 1. Cow grazing in the field | Position of cow is changing with time. | Tree | Remains at a fixed place. |
| 2. A walking man | Position of man is changing with time. | House | Remains at a fixed place. |
| 3. A flying bird | Position of bird is changing with time. | School | Remains at a fixed place. |
| 4. A moving train | Position of train is changing with time. | Factory | Remains at a fixed place. |
| 5. Earth | Position of earth is changing with time | Electric pole | Remains at a fixed place. |
Result : Cow grazing in the field, a walking man, flying bird, moving train, earth are all in motion.
Conclusion : An object is said to be in motion if its position changes with respect to the reference point with time. If an object is not changing its position with respect to the reference point with time, it is said to be at rest.
Activity 3.
Aim : To explore linear motion.
Materials Required: Eraser.
Procedure :
- Take an eraser and drop it from a certain height.
- Observe the motion.
Observations: It moves along a straight line.
Conclusion: The motion of the erasar dropped from a certain height is linear motion.
The motion of a stone dropped from a certain height, the motion of a car along a straight road, movement of the drawer of a table, motion of a striker on the carrom board, etc are the examples of linear motion.
Activity 4.
Aim : To explore circular motion.
Materials Required : Earser, thread
Procedure :
- The an eraser at one end of a thread.
- Hold the other end of the thread with your hand and whirl it.
Observation : The eraser moves along a circular path.
Conclusion: Whirling of an eraser tied to a string is an example of circular motion.
Activity 5.
Aim : To investigate oscillatory motion of an eraser.
Materials Required : Eraser, thread.
Procedure :
- Tie an eraser at one end of a thread.
- Hang the eraser by holding the other end of the thread. Keep your hand steady. [Fig. 11 (a)]
- Using the other hand, take the eraser slightly to one side and then release.
Observations: Eraser starts moving to and fro.
Conclusion : The to-and-fro motion of a body along the same path is called oscillatory motion.
Activity 6.
Aim : To investigate oscillatory motion of a metal strip.
Materials Required : A metal strip ( 50 cm long), books or a brick.
Procedure:
- Take a thin metal strip of about 50 cm long.
- Hold its one and pressed to a table.
- Press the free end of the strip slightly and let it go.
- Observe the motion of this end of the strip.
Observation: The metal strip moves up and down.
Conclusion: When an object moves to and fro about some fixed position, its motion is oscillatory motion.
Activity 7.
Aim : To identify different kinds of motion and classify them as linear circular or oscillator.
Materials Required: A picture of a children’s park.
Procedure :
- Look at the picture of a children’s park.
- Observe different kinds of motions.
Observation:
| Object | Linear motion | Circular motion |
Oscillatory motion moving to and fro | Justification |
| 1. Swing | ✓ | To and fro motion along the some path. | ||
| 2. Merry to round | ✓ | Object moves along a circular path. |
Conclusion: There are many different kinds of motions.