Physics
(a) Describe in steps how would you measure the length of a pencil using a metre ruler. Draw a diagram if necessary.
(b) Explain with an example how you will use the metre ruler in part (a) if the ends of the ruler are broken.
Measurements
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Answer
(a) Following are the steps to measure the length of a pencil :
- To measure the length of a pencil with a metre ruler, the ruler is placed with its markings close to the object.
- Then the zero mark on the ruler is made to coincide with one end of the object which is point P.
- Now the position of the other end (which is Q) of the object is read on the ruler from vertically above position to minimize parallax error as it can be seen from figure below.
- This reading gives the length (PQ) of the pencil.
(b) When the ends of the ruler get damaged with use and its zero mark may not be visible then 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 of the two readings gives the length of the object which you can see from below image.
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