MOTION AND MEASUREMENT OF DISTANCES

2.

(i) by the invention of

(ii) by the invention of

3.

4.

6.

7.

Each metre (m) is divided into 100 equal divisions, called centimeter (cm). Each

Centimeter has ten equal divisions, called millimeter (mm). Thus

1 m = 100 cm

1 cm = 10 mm

For measuring large distances, metre is not a convenient unit. We define a larger

unit of length. It is called kilometer (km).

1 km = 1000 m.

8.

1 decametre = 10 m

1 hectometre = 100 m

1 kilometre = 1000 m

9.

For example, milli, centi, deci.

1 m = 10 decimetre

1 m = 100 centimetre

1 m = 1000 millimetre.

10.

(1) Place the scale in contact with the object along its length.

(2)

(i) Avoid taking measurements from zero mark.

(ii) Use any other full mark of the scale, say 1.0 cm [Fig. 10.4 (a)].

(iii)Subtract the reading of this mark from the reading at the other end. For example, in Fig. 10.4 (b), the reading at starting mark is 1.0 cm and at the other end it is 6.5 cm. Therefore, the length of the object is (6.5 – 1.0) cm = 15.5 cm.

(3) Correct position of the eye is also important for making measurement. Your eye must be exactly above the point where the measurement is to be taken. Position ‘A’ is the correct position of the eye. Note that from position ‘A’, the reading is 1.0 cm. From positions ‘B’ and ‘C’, the readings may be different.

13.

14.

15.

(i) When a body moves in a circular path, its motion is known as circular motion.

(ii) Example : i. motion of stone tied in a thread and whirled.

ii. motion of a blade of an electric fan.

iii. motion of second’s hand in a clock.

(iii)In circular motion, the object remains at the same distance from a fixed point.

17.

18.

Example : (i) Oscillations of a pendulum.

(ii) Motion of a swing.

(i) Motion of a ball on the ground. Here, the ball is rotating about an axis but the axis itself is moving along a straight line. Thus, the ball executes a rectilinear motion as well as rotational motion.

(ii) Motion of earth – earth executes rotations on its axis and also revolves around the sun.

20.

21.

(i) It involves the comparison of an unknown quantity with some known quantity of the same kind.

(ii) This known fixed quantity is called

(iii) The result of measurement is expressed in two parts. One part is a number. The other part is the unit of measurement.

(ii) Water – Ship, Boat

(iii) Air – Aeroplane, Helicopter.

Q.2. Fill in the blanks :

(i) One metre is ………. cm.

(ii) Five kilometer is ………. m.

(iii) Motion of a child on a swing is ……… .

(iv) Motion of the needle of a sewing machine is ………. .

(v) Motion of wheel of a bicycle is ……….. .

Ans.

(ii) 5000

(iii) Periodic (oscillatory motion)

(iv) Periodic motion

(v) Circular motion.

Ans.

Q.4. Arrange the following lengths in their increasing magnitude:

1 metre, 1 centimetre, 1 kilometre, 1 millimetre.

Ans.

Q.5. The height of a person is 1.65 m. Express it into cm and mm.

Ans.

We have to find out (a) height in cm

(b) height in mm.

(a) We know that,

1 m = 100 cm

Hence, 1.65 m = 1.65 × 100 cm

(b) Again we know that,

1 m = 1000 mm

Hence, 1.65 m = 1.65 × 1000 mm

Or

We known that,

1 cm = 10 mm

Hence, 165 cm = 165 × 10 mm

Ans.

Distance between Radha’s home and her school = 3250 m

We have to find out distance in km.

We know that,

1000 m = 1 km

Hence, 3250 m = km

Ans.

Reading at starting end = 3.0 cm

Reading at other end = 33.1 cm

We know that,

Length of the object = (Reading at other end – Reading at starting end)

Hence, Length of the needle = 33.1 – 3.0 cm

Q.8. Write the similarities and differences between the motion of a bicycle and a ceiling fan that has been switched on.

Ans. (i) Similarity :

Q.9. Why could you not use an elastic measuring tape to measure distance? What would be some of the problems you would meet in telling someone about a distance you measured with an elastic tape?

Ans.

Q.10. Give two examples of periodic motion.

Ans.

(i) Motion of the earth around the sun.

(ii) Oscillations of a pendulum.

Q.1. Is the hour hand of a wall clock at rest or in motion?

Ans.

Q.2. Is your classroom at rest or in motion?

Ans.

Q.3. What is the system used for measurements now-a-days?

Ans.

Q.4. Name the unit of length, which should be used to express the thickness of a coin.

Ans.

Q.5. Name the unit of length, which you would like to use while expressing the distance between Delhi and Lucknow.

Ans.

Q.6. Name the SI unit of length.

Ans.

Q.7. What do you understand by unit?

Ans.

Q.8. What is the convenient unit to measure the distance between two cities or villages?

Ans.

Q.9. What is measurement?

Ans.

Q.10. Name the two parts which must be mentioned to state the results of a measurement.

Ans.

Q.11. Which unit should be used to express thickness of coin or wire?

Ans.

1 mm = 10

Q.12. List three uses of metre.

Ans.

Q.13. Can you measure the length of a pencil with metre-scale?

Ans.

Q.14. What is estimation?

Ans.

Q.15. Explore and find out what kind of scale is used by cloth merchants, tailors, carpenters and mechanics to measure length.

Ans.

Carpenters use plastic metre tape and iron metre scale both.

Ans.

Q.17. Why do we lean forward with a jerk when the bus driver applies brakes in a moving bus?

Ans.

Q.18. If you are sitting in a moving bus, are you rest or in motion?

Ans.

Q.19. What type of measuring device would you use to measure the girth of a tree?

Ans.

Q.20. 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?

Ans.

Q.21. State two precautions, which should be taken while using a metre scale to measure the length of an object.

Ans.

(i) Place the scale in contact with the object along its length.

(ii) Most important, eye should be correctly positioned above the point to be measured to make a correct measurement. (See Fig. 10.5)

Q.22. Using a thread how will you find the circumference of a one rupee coin.

Ans.

Q.23. Why a cubit can not be used as the standard unit of length?

Ans.

Q.24. Describe the method you would use to find the thickness of a sheet of paper of your science book.

Ans.

Take 100 sheets of paper together. Find their combined thickness by using a centimeter scale. Divide the total thickness by the number of sheets. It is the thickness of asingle sheet.

For example : If the thickness of 100 sheets = 1.5 cm.

Thickness of a single sheet = = cm

Q.25. What precaution should be taken while buying something?

Ans.

Q.26. Can you measure the diameter of a ball with the help of metre scale?

Ans.

Ans.

Ans.

Thickness of 1 coin = = cm

Q.29. What does your P.T. teacher use to measure the length of the playground?

Ans.

Q.30. Fill in the blanks :

a) 1 cm = ……….. mm.

b) 1 dm = ……….. metre.

c) 1 kilometre = ………… metre.

d) 1 metre = ……….. centimeter.

Ans.

b) 1/10

c) 1000

d) 100

Q.31. 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.

Ans.

b) 1 millimetre < 1 centimetre.

c) 1 hectometre < 1 kilometre.

d) 1 decimetre > 1 centimetre.

Q.32. Group the following into moving and stationary objects:

(i) House top

(ii) Clock

(iii)Minute hand of the clock

(iv)Bird sitting on the roof

(v) Flying bird

(vi)Table

Ans.

Moving Objects | Stationary Objects |

Minute hand of the clock, Flying bird | House top, clock, Bird sitting on the roof, Table |

Ans.

Ans.

Q.35. How will you measure the length of any curved line?

Ans. To measure the length of

Ans.

(b) Curvilinear motion.

(c) Random motion.

(d) Vibrational motion. (a kind of Periodic motion).

Q.1. Match the following items given in Column A with that in Column B :

Column A | Column B |

(a) Metre (b) Yard (c) Hand Span (d) Least Count (e) Millimetre (f) Kilometre (g) Rest (h) Motion (i) Circular Motion (j) Rectilinear Motion (k) Rotational Motion (l) Periodic Motion | (i) Unit used to measure very small distances. (ii) Unit used to measure large distances. (iii) SI unit of length. (iv) Non-standard unit of length. (v) Standard unit of length. (vi) Apple falling from a tree. (vii) Motion of the tip of the blade of a fan. (viii) Motion of a pendulum. (ix) Motion of a top. (x) State of moving objects. (xi) State of stationary objects. (xii) Minimum amount that can be measured by a device. |

(i)

Q.3. State whether the statements given below are True or False :

Q.4. Choose the correct option in the following questions :

(i)

(a) Angul (finger) (b) Mutthi (fist)

(c) Step (d) Inch

(ii)

(a) Metre (b) Centimetre

(c) Kilometre (d) All of these

(iii)

(a) 4,00,000 metre (b) 40,000 metre

(c) 4,000 metre (d) 400 metre

(iv)

(a) 150 mm (b) 15 mm

(c) 1.5 mm (d) 0.15 mm

(v)

(a) 1 m = 100 cm (b) 1 cm = 100 mm

(c) 1 km = 100 m (d) all of these

(vi)

(a) C (b) B

(c) A (d) Any way can be chose

(vii)

(a) apple falling from a tree (b) motion of a car on road

(c) a spinning top (d) both (a) and (b)

(viii)

(a) Oscillations of a pendulum (b) Motion of a bus on road

(c) A spinning top (d) A stone dropped from a certain height

(ix)

(a) Oscillatory motion (b) Vibratory motion

(c) Circular motion (d) Linear motion

(x)

(a) 10 (b) 1000

(c)100 (d) 10000

Q.1. Match the following items given in Column A with that in Column B :

Column A | Column B |

(a) Metre (b) Yard (c) Hand Span (d) Least Count (e) Millimetre (f) Kilometre (g) Rest (h) Motion (i) Circular Motion (j) Rectilinear Motion (k) Rotational Motion (l) Periodic Motion | (iii) SI unit of length. (v) Standard unit of length. (iv) Non-standard unit of length. (xii) Minimum amount that can be measured by a device. (i) Unit used to measure very small distances. (ii) Unit used to measure large distances. (xi) State of stationary objects. (x) SI unit of length. (vii) Motion of the tip of the blade of a fan. (vi) Apple falling from a tree. (ix) Motion of a top. (viii) Motion of a pendulum. |

(i) straight line (ii) rectilinear (iii) circular

(iv) periodic (v) oscillatory (vi) wheel

(vii) unknown, known (viii) Greeks (ix) metric

(x) S.I. (xi) centimeter (xii) ten

(xiii) position (xiv) periodic (xv) rotational.

(i) False (ii) True (iii) True (iv) True

(v) False (vi) False (vii) True (viii) True

(ix) False (x) True (xi) True (xi) True.

(i) (d) All other units vary from person to person.

(ii) (a) All other are multiples of metre.

(iii) (c) 1 km = 1000 m, 4 km = 4000 m

(iv) (a) 1 cm = 10 mm, 15 cm = 150 mm

(v) (d) 1 m = 100 cm.

(vi) (c) B and C are incorrect positions.

(vii) (a) apple falling from tree and motion of a car on road is the example of

rectilinear motion.

(viii) (a) Osillation is an example of periodic motion.

(ix) (a) The to-and-fro motion of a body along the same path is called oscillatory

motion.

(x) (b) 1 metre = 1000 millimetre.