Place the marked end of the thread at the beginning of the curved line and press it down with your thumb. Why do we need to press the thread?
Answers
We cannot measure the length of a curved line directly by using a metre scale. We can use a thread to measure the length of a curved line.
Method to measure length using string
Use a thread to measure the length of the curved line AB. Put a knot on the thread near one of its ends.Place this knot on the point A. Now, place a small portion of the thread along the line, keeping it taut using your fingers and thumb. Hold the thread at this end point with one hand. Using the other hand, stretch a little more portion of the thread along the curved line. Go on repeating this process till the other end B of the curved line is reached.Make a mark on the thread where it touches the end B. Now stretch the thread along a metre scale. Measure the length between the knot in the beginning and the final mark on the thread. This gives the length of the curved line AB.
CORRECT AND INCORRECT METHOD OF PLACING A SCALE FOR MEASUREMENT OF LENGTH - SHORTCUT
concept
In taking measurement of a length,we need to take care of the following:
Place the scale in contact with the object along its length.
In some scales, the ends may be broken. You may not be able to see the zero mark clearly.In such cases, you should avoid taking measurements from the zero mark of the scale. You can use any other full mark of the scale. Then you must subtract the reading of this mark from the reading at the other end. For example, if the 1st mesurement taken as 1cm and end measure taken as 13.2 cm.then the actual length is found out as 13.2-1 = 12.2 cm.
Your eye must be exactly in front of the point where the measurement is to be taken.
MEASUREMENT OF LENGTH - DEFINITION
Generally a metre rule having its zero mark at one end and 100 cm mark at the other end is used to measure the length of an object. It has 10 subdivisions in each one centimetre length, so the value of its one small division is 1mm. Thus a metre rule can be used to measure length with still more accuracy i.e., up to second decimal place of centimetre. The reason is that if one end of object lies between two small divisions on metre rule, the mark nearer the end of the object is read and thus its length correct up to the second decimal point can not be measured. However, it becomes possible with the help of vernier callipers and screw gauge. They are more accurate since they have least count smaller than 0.1 cm.
Because otherwise the thread may move away while u work. These are odd questions U press it so that it sticks at the desired point, that is, the beginning of the curved line.
Later u slowly put the thread perfectly along the curved line. U mark it where the other ending point of the curved line touches the thread, and then freely hold the thread (straightly not curvedly) along a ruler to measure the length between the 2 already marked points (on the thread) or length of the curved line.
