1. History Of Transport -
ü Invention of the wheel made a great change in modes of transport. The design of the wheel was improved over thousands of years.
ü Animals were used to pull carts that moved on wheels. Until the beginning of the 19th century, people still depended on animals, boats and ships to transport them from place to place.
ü The invention of steam engine led to the development of new means of transport. Railroads were made for steam engine driven carriages and wagons. automobiles such as motor cars, trucks and buses.
ü Motorized boats and ships were used as means of transport on water. The early years of 1900 saw the development of aeroplane. These were later improved to carry passengers and goods.
ü Electric trains, monorail, supersonic aeroplane and spacecraft are some of the contributions of the 20th century.
2. Distance And Displacement -
ü The actual path traveled by any moving body is called as its distance.
ü The shortest path between initial and final point for any moving body is its displacement.
ü Both distance and displacement are measured in terms of length.
ü The unit of measurement is centimeter, meter, kilometer etc.
3. Standard Units Of Measurement -
ü Cubit was accepted as a standard unit in Egyptian system. A cubit meant the length between fingertips and elbow. Considering the differences in the length of body parts based on age and body type of an individual, these arbitrary systems became non reasonable.
ü Other units used earlier were ‘foot’, end of outstretched arm and chin, fist, etc.
ü The CGS (centimeter, gram, second) system- In the CGS system of measurement length is measured in centimeters, the mass of the body or substance is measured in grams and time is measured in seconds. Thus centimeter, gram and seconds are the fundamental units of measurement in the CGS system.
ü MKS (meter, kilogram, second) system- In MKS system or metric system, the unit of measurement for length is meter, for mass it is kilogram and for time it is seconds. Thus in this system meter, kilogram and seconds are fundamental units of measurement. This system was used in France and number of other European countries.
ü FPS (foot, pound, second) system- In this system the unit of measurement for length is foot, for mass it is pound and for time it is second. This system is used commonly in Britain and the countries that were under its rule.
ü Nowadays, the International System of units or the SI units have been accepted all over the world as a standard unit of measurement.
ü Some important conversions between CGS and MKS system -
1 m = 100 cm
1 kg = 1000 g
1s = 1/60 min
4. Hand-span Method -
ü The measurement taken by stretching a hand and measuring number of stretch from one end to another end of an object that is to be measured.
ü Measuring using hand-span is not so reliable and hence some standard units of measurement have been introduced.
5. How To Use A Mater Scale?
Step 1: Keep the scale in contact with the object that is to be measured.
Step 2: Place the scale on object. Start measuring from the 0 mark of the scale.
Step 3: To avoid taking incorrect measurements the eye position should be correct.
6. Types of Motion -
ü Whenever a body changes its position with respect to time then the body is said to be in motion.
ü Rectilinear Motion - When an object moves along a straight line, it is said to be undergoing rectilinear motion also called as straight line motion . For Example- A train moving along a railway track.
ü Circular Motion - The motion exhibited by the hands of a clock is called Circular Motion. The body moves around a fixed circular path called circumference.
ü Periodic Motion - When an object repeats its motion after a fixed interval of time it is said to be undergoing periodic motion. Also the to and fro motion of an object is called periodic motion. For Example- Pendulum.
ü Rotational Motion - This motion can be easily understood by imagining Earth’s rotation. When the Earth spins on its own axis it is said to be undergoing rotational motion.
NCERT PRACTICE QUESTIONS
1. Give two examples each, of modes of transport used on land, water and air.
Ans. - Land- Train, bus. Water- Ship, Boat. Air- Helicopter, Air-balloon.
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.- (i)100 cm. (ii) 5000 m. (iii) periodic. (iv) periodic. (v) circular.
3. Why can a pace or a footstep not be used as a standard unit of length?
Ans.- Pace or a footstep cannot be used as a standard unit of length because it varies from person to person based on age and body type of an individual.
4. Arrange the following lengths in their increasing magnitude: 1 metre, 1 centimeter, 1 kilometer, 1 millimeter.
Ans. - 1 millimeter, 1 centimeter, 1 metre, 1 kilometer
5. The height of a person is 1.65 m. Express it into cm and mm.
Ans.- 1.65 = 165 cm = 1650 mm
6. The distance between Radha’s home and her school is 3250 m. Express this distance into km.
Ans.- 1km = 1000 m, thus 3250 m = 3.25 km.
7. While measuring the length of a knitting needle, the reading of the scale at one end is 3.0 cm and at the other end is 33.1 cm. What is the length of the needle?
Ans.- Length of needle = 33.1 – 3 = 30.1 cm
8. Write the similarities and differences between the motion of a bicycle and a ceiling fan that has been switched on.
Ans.- Similarity- Both show circular motion. Difference- Bicycle wheels move in rectilinear motion, but the fan does not move in rectilinear motion.
9. Why would you not like to use a measuring tape made of an elastic material like rubber to measure distance? What would be some of the problems you would meet in telling someone about a distance you measured with such a tape?
Ans.- An elastic measuring tape will not give accurate measurement as it stretches in length and reduces back in size when de-stress. When we express measurement taken with elastic tape, we have to tell whether the tape was stretched or de-stress.
10. Give two examples of periodic motion.
Ans.- A needle of a sewing machine, a pendulum.
Junior Science Topic - Motion And Measurement Of Distance. Chapter notes, video lectures, power point presentation and NCERT exercise solution. (Class 6, CBSE syllabus, chapter 10)
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