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Question
Describe in steps how would you measure the length of a pencil using a metre rule. Draw a diagram if necessary.
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Solution
To measure the length of a pencil using a metre rule, place metre rule with its marking close to the object. Let PQ be a pencil.
The end P of the pencil coincides with the zero marks on the ruler. The end Q of the pencil is read by keeping the eye at the position ‘B’ vertically above the end Q. So the length of the pencil is 4.3 cm.
Explain with an example of how you will use the metre ruler in part (a) if the ends of a ruler are broken.
Ans. The ends of the ruler get damaged with use and its zero marks may not be visible. To measure the length of an object with such a ruler, the object is placed close to a specific marking on the ruler and positions of both ends of the object are read on the ruler.
The difference between the two readings gives the length of the object. In fig. the reading on the ruler at the end X is 1.0 cm and at the end, Y is 4.3 cm. So the length of the rod XY is 4.3 — 1.0 = 3.3 cm.
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