# User Forum

Subject :NSO    Class : Class 6

Which one of these is true about measuring length using a ruler scale? The position of eye should be
a. Vertically above the 0-end
b. Vertically above the point where the measurement is to be taken
c. Anywhere according to one's convenience.

Ab. only
Ba. only
Ca. and b.
Db. and c.

Isn't option c correct?

## Ans 1:

Class : Class 7
no because what will u do of zero u have to

Class : Class 8

Class : Class 6

## Ans 4:

Class : Class 6
it is simple that while measuring, at first you eye must be vertically above 0

## Ans 5:

Class : Class 6
the answer will be both a and b

Class : Class 6
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## Ans 7:

Class : Class 8
I think it should be C because otherwise the zero end can shift slightly (in our viewpoint) and measurement will be wrong. So both statements a and b are correct and the answer is C.

Class : Class 8

## Ans 9:

Class : Class 3
No guys. Human eye can't focus simultaneously on two points. To avoid parallax error , eye should be on the point of measurement to be taken.Hence given answer is correct in my view. You may comment.

## Ans 10:

Class : Class 7
No as it causes a parallax error. It should be option A. If you don't believe me then try it yourself with a scale and measuring a line segment from different eye positions. You will see that, the measurement varies slightly every time. That's why option A is correct.