The standard unit of length is metre. Why is the distance between two cities or two different location measured in kilometre? (a)Because meter gives larger value than kilometre.(b)Because the kilometre is more accurate than metre.(c)Because measurement in kilometre is easy to measure for larger distances.(d)Because measurement in kilometre does not need any device.
Answers
Answer:
The option will be C
Explanation:
because measurement in kilometer is easy to measure for larger distance
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Answer:
In ancient time man used to move only on foot and carry goods either on his back or on the back of some animals.
2. A great change in the modes of transport was made :
(i) by the invention of wheel.
(ii) by the invention of steam engine.
3. Measurement : It is the technique developed for correct judgement of dimensions of various objects.
4. Non-standard measures : The lengths of steps, arms, hands, or fingers of different people are different, therefore the distance measured with their help is not always reliable. These methods are therefore called non-standard measures.
5. Standard measures : Measures that are the same all over the world are known as standard measures.
6. SI units : In October 1960, the XIIth general conference on weight and measures adopted in International system of units. “The System International Units” is the set of units to maintain uniformity all over the world.
7. Metre : It is the standard unit of length. The symbol of metre is m.
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. Simple multiples of units : Units used for the measurement of larger distances are the multiples of SI unit. For example : deca, hector, kilo.
1 decametre = 10 m
1 hectometre = 100 m
1 kilometre = 1000 m
9. Sub-multiples of units : Units used for measuring smaller distances are the submultiples of SI units.
For example, milli, centi, deci.
1 m = 10 decimetre
1 m = 100 centimetre
1 m = 1000 millimetre.
10.Making measurement of a length : In making measurement of length of an object we should follow the following procedure :
(1) Place the scale in contact with the object along its length.
(2) Measurement with a scale with broken ends
(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.
11.Least count : A scale is marked in centimeters and millimeters . With the scales of this kind we can measure correctly upto one millimeter, that is one-tenth of a centimeter. This is called the least count of a (15 cm) scale.
12.Measuring the length of a curved line : We can not measure the length of a curved line directly by using a metre scale. We can use a thread or divider to measure the length of a curved line.
13.Motion : It is a state of objects in which they are changing their place with time.
14.Rest : All the stationary objects which are not in motion, that is, do not change their place with time are said to be at rest.
15.Rectilinear motion : When the objects change their position with time along a straight line, this type of motion is called rectilinear motion.
Explanation:
correct opsion is D.
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