Answer: (d) Inch
Explanation:
All other units vary from person to person

Answer: (a) Metre
Explanation:
All other are multiples of metre.

Answer: (c) 4,00p metre
Explanation:
1 km = 1000 m, 4 km = 4000 m

Answer: (a) 150 mm
Explanation:
1 cm = 10 mm, 15 cm = 150 mm

Answer: (d) all of these
Explanation: 1 m = 100 cm.

Answer: (c) A
Explanation:
B and C are incorrect positions.

Answer: (d) both (a) and (b)
Explanation:
Apple falling from a tree and motion of a car on road are the examples of rectilinear motion.

Answer: (a) Oscillation of a pendulum
Explanation:
Oscillation of a pendulum is an example of periodic motion.

Answer: (a) Oscillatory motion
Explanation:
The to-and-fro motion of a body along the same path is called oscillatory motion.

Answer: (b) 1000
Explanation:
1 metre = 1000 millimetre.

Answer:

Answer: straight line

Answer: rectilinear

Answer: circular

Answer: periodic

Answer: Oscillatory

Important Questions

Question 1.
Name the invention which made a great change in modes of transport.
Answer:
Invention of wheel.

Question 2.
Which power was used to pull vehicles in ancient times?
Answer:
Animals were used to pull vehicles in ancient times.

Question 3.
Define rest and motion.
Answer:
An object that does not change its positions with time is said to be at rest.
An object that changes its positions with time is said to be in motion.

How far have you travelled? How wide is this desk?

Question 1.
Why is it important to know how far a place is?
Answer:
It is important to know how far a place is, so that we can have an idfea how we are going to reach that place – walk, take a bus or train, a ship, an aeroplane or even a spacecraft. ‘

Question 2.
What does your P.T. teacher use to measure the length of the playground?
Answer:
My P.T. teacher has plastic made tape scale to measure the length. Its total length is 100 metre. It can be rounded up in round box.

Question 3.
What is estimation?
Answer:
To guess the dimensions of an object without actual measuring is known as estimation. It is difficult to make near about correct estimate. It needs a lot of experience.

Question 4.
Explore and find out what kind of scale is used by cloth merchants, tailors, carpenters and mechanics to measure length.
Answer:
Cloth merchants use iron/steel metre scale.
Tailors use plastic metre scale tape.
Carpenters use plastic metre tape and iron metre scale both.

Question 5.
Differentiate between distance and displacement.
Answer:
Distance: The total length travelled from one point to another.
Displacement: It is the shortest distance travelled from one point to another.

Some measurements

Question 1.
What is measurement?
Answer:
Measurement is the technique developed for correct judgement of dimensions of various objects.

Question 2.
What do you understand by unit?
Answer:
A quantity adopted as a standard of measurement of a physical quantity is called unit.

Question 3.
Name the two parts which must be mentioned to state the results of a measurement.
Answer:
Magnitude and unit are the two parts which must be mentioned to state the results of a measurement.

Question 4.
What type of measuring device would you use to measure the girth of a tree?
Answer:
Measuring tape is suitable to measure the girth of a tree.

Standard units of measurements

Question 1.
What is the system used for measurements nowadays?
Answer:
S.I. system.

Question 2.
Name the unit of length, which should be used to express the thickness of a coin.
Answer:
Millimetre (mm).

Question 3.
Name the unit of length, which you would like to use while expressing the distance between Delhi and Lucknow.
Answer:
Kilometre (km).

Question 4.
Name the SI unit of length.
Answer:
Metre (m).

Question 5.
What is the convenient unit to measure the distance between two cities or villages?
Answer:
Kilometre (1 km = 1000 m).

Question 6.
Which unit should be used to express thickness of coin or wire?
Answer:
Very small length like thickness of coin or wire is expressed in millimetres (mm).
1 mm = 10^-3 m or 10³ mm = 1 m.

Question 7.
Why a cubit cannot be used as the standard unit of length?
Answer:
Length of hand and cubit are not same for all the people. So these cannot be used as the standard unit of length.

Question 8.
Define cubit and foot.
Answer:
Cubit is the length between the tip of the elbow and the middle finger.
The length of the foot of a person is called foot.

Question 9.
Fill in the blanks:
(a) 1 cm = …………… mm.
(ft) 1 dm = ………….. metre.
(c) 1 kilometre = …………… metre.
(d) 1 metre =……………….. centimetre.
Answer:
(a) 10
(b) 1/10
(c) 1000
(d) 100

Question 10.
Fill in the blanks with < or > sign.
(a) 1 decametre ………………1 decimetre.
(b) 1 millimetre ………………1 centimetre.
(c) 1 hectometre ………………1 kilometre.
(d) 1 decimetre ………………1 centimetre.
Answer:
(a) 1 decametre > 1 decimetre.
(b) 1 millimetre < 1 centimetre.
(c) 1 hectometre < 1 kilometre.
(d) 1 decimetre > 1 centimetre.

Correct measurement of length

Question 1.
List three uses of metre.
Answer:
Metre can be used as a unit to measure

1. the length of a room
2. the height of a tree or a building or
3. the length and breadth of a playground.

Question 2.
Can you measure the length of a pencil with metre-scale?
Answer:
No, length of pencil cannot be measured with metre scale. To measure the length of a pencil, a small scale, like six inches plastic scale should be used. This length should be expressed in centimetres.

Question 3.
A 30 cm scale has one end broken. The mark at the broken end is 2.6 cm. How would you use it to measure the length of your pencil?
Answer:
Put one end of the pencil at nearest full mark say 3.0 cm in this case. Take the reading of the other end. Now subtract 3 from the previous reading and this will be the required length of pencil.

Question 4.
State two precautions, which should be taken while using a metre scale to measure the length of an object.
Answer:
Two precautions are:

1. Place the scale in contact with the object along its length.
2. Most important, eye should be correctly positioned above the point to be measured to make a correct measurement.

Question 5.
Describe the method you would use to find the thickness of a sheet of paper of your science book.
Answer:
It is not easy to measure the thickness of a single sheet of paper by using metre scale. The method used to find the thickness of a single sheet is as follows:

Take 100 sheets of paper together. Find their combined thickness by using a centimetre scale. Divide the total thickness by the number of sheets. It is the thickness of a single sheet.
For example: If the thickness of 100 sheets = 1.5 cm.

Thickness of a single sheet

= 0.015 cm.

Question 6.
What precaution should be taken while buying something?
Answer:
While buying clothes, pipes, laces, it should be checked whether the scale is correct or not. A correct metre has signs (⟷) on both the ends in addition to the stamp of the weight and measure department. The metre scale may have been cut off. In such a case short measurement is resulted.

Question 7.
Can you measure the diameter of a ball with the help of metre scale?
Answer:
Yes, the diameter of a ball can be measured correctly with the help of metre scale. It is one of the ways in which diameters of spherical surface can be measured easily. In this method, the two wooden blocks A and B must be exactly parallel to each other (Fig. 10.11).

Question 8.
How will you find the thickness of a thin wire?
Answer:
Take a round pencil and wrap the given wire round the pencil making 25 turns forming a coil. Measure the length of the so formed coil. Divide the total length of the coil by number of turns. This is the thickness of the wire.

Question 9.
How would you measure the thickness of a coin?
Answer:
Take ten coins and put them one over another. Find the total thickness of ten coins with the help of a scale. Divide the total thickness by the number of coins (Fig. 10.13).

=0.24 cm

Measuring the length of a curved one