Class 6 || Science || Ch. 10. Give two examples of periodic motion.
Q. How how the invention of wheel made a great change in mode of transport?
Ans. Long ago people did not have any meansof transport. They used to move only onfoot and carry goods on their back.
Invention of the wheel made a great
change in modes of transport. Thedesign of the wheel was improved overthousands of years. Animals were usedto pull carts that moved on wheels.
Now a days we can see many types of the vehicles moves on the wheels. Without wheel we cannot think about this world.
Q. What do you mean by the means of the transport ?
Ans. The means of transport refers to the vehicles necessary for transport according to the chosen mode - airplane, ship, truck and rail.
Q. What are main types of mode of transportation?
Ans. These are five most common modes of transport : railways, roadways, airways, waterways and pipelines.
Q. Draw a path of development of transport?
Ans. In ancient times people use animals cards and boards to carry loads.
After the inventionof steam engine led to the developmentof new means of transport. Railroadswere made for steam engine drivencarriages and wagons.
Later came automobiles such as motor cars, trucksand buses. Motorised boats and ships wereused as means of transport on water.
Electrictrains, monorail, supersonic aeroplanesand spacecraft are some of thecontributions of the 20th century.
Q. What do you mean by measurement?
Ans. Measurement means thecomparison of an unknown quantity with some known quantity. This knownfixed quantity is called a unit.
In 1790, the French created a standard
unit of measurement called themetric system.
Thesystem of units now used is known as
the International System of Units (SIunits). The SI unit of length is a metre.
1m = 10dm = 100cm = 1000mm
1dm = 10cm = 100mm
1cm = 10mm
Periodic Motion.:- Motion which repeats itself after certain intervals of time is called periodic motion. Since the motion of a swing also repeats after regular intervals so, the motion of child on a swing is periodic.
Circular Motion:- When an object moves in such a way that its distance from a fixed point remains the same, it is said to have circular motion.
Since, the wheel of a bicycle rotates about its central part which remains fixed as the bicycle moves hence, the wheel possesses circular motion.
NCERT Solution for Class 6 Science
Chapter 10 - Motion and Measurement of Distances
1. Give two examples each of modes of transport used on land, water, and air.
Ans. Examples of modes of transport used on Land: Bus, car, train, truck
Water: Ship, boat
Air: Aeroplane, helicopter
2. Fill in the blanks:
(i) One metre is __________ cm.
(ii) Five kilometres 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___________.
Answer.
(i) One metre is 100 cm.
(ii) Five kilometres is 5000 m.
(Explanation:
We know that 1 km = 1000 m
5 km = 1000 × 5 = 5000 m
(iii) Motion of a child on a swing is periodic.
(iv) Motion of the needle of a sewing machine is periodic.
(v) Motion of the wheel of a bicycle is circular motion.
3. Why can a pace or a footstep not be used as a standard unit of length?
Ans. Because the size of pace or footstep of different people are different so the lengths measured by two different persons using their footsteps will not be the same. Due to this reason pace or a footstep cannot be used as a standard unit of length
4. Arrange the following lengths in their increasing magnitude:
1 metre, 1 centimetre, 1 kilometre, 1 millimetre
Answer.
1 m = 100 cm
1 cm = 10 mm
1 m = 100 × 10 = 1000mm
Now, 1 km = 1000 m
1 km = (1000 × 100)cm = 100000 cm = (100000 × 10)mm = 1000000mm
So, arranging 1 metre, 1 centimetre, 1 kilometre, 1 millimetre in increasing order we have:
1mm < 10mm < 1000mm < 1000000mm
Or 1 millimetre < 1 centimetre < 1 metre < 1 kilometre
5. The height of a person is 1.65 m. Express this in cm and mm.
Answer.
Height of the person = 1.65 m
We know that 1 m = 100 cm
1.65 m = 100 × 1.65 = 165 cm
Again, 1 m = 100 cm = 1000 mm
1.65 m = 1.65 × 1000 = 1650 mm
Thus height of person in cm = 165 cm
And height of person in mm = 1650 mm
6. The distance between Radha’s home and her school is 3250 m. Express this distance in km.
Ans. The distance between Radha’s home and her school is 3250 m.
We know that 1 km = 1000 m
Or 1000 m = 1 km
Or 1m = 1/1000 Km
Thus, 3250 m = (1/1000) X 3250 = 3.25 Km
Therefore, distance between Radha’s home and her school in km = 3.25 km
7. While measuring the length of a knitting needle, the reading of the scale at one end is 3 cm and at the other end is 33.1 cm. What is the length of the needle?
Ans. Length of the knitting needle is the difference between two readings.
Thus, length of knitting needle = 33.1− 3.0 = 30.1 cm
8. Write the similarities and the differences between the motion of a bicycle and a ceiling fan that has been switched on.
Ans. Similarity between the motion of a bicycle and a ceiling fan is that both the wheels of bicycle and the fan are moving around a fixed point and possess circular motion.
Differences between the motion of a bicycle and a ceiling fan is that a bicycle has linear motion as it moves forward, whereas ceiling fan does not possess the linear motion.
9. Why can 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?
Answer.
Elastic tapes are stretchable. So, the length of an elastic measuring tape will change each time due to stretching. So, it will not give correct measurement of a distance. Therefore, we cannot use an elastic measuring tape to measure distance. While measuring the distance with an elastic tape, we will get different values of the same distance each time.
10. Give two examples of periodic motion.
Ans. Examples of periodic motion are: (any two)
Motion of a pendulum, Motion of a swing, Motion of Earth round the Sun, Motion of a rocking chair etc.
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