Answer:
A quantity that has magnitude and direction. It's usually represented by an arrow whose direction is the same direction is the same as that of the quantity and whose length is proportional to the quantity's magnitude
The focal length of a lens needed by a woman whose near point is 50cm from her eyes is 50cm.
To find the answer, we have to know about the focal length of correcting lens.
<h3>
How to find the focal length of
correcting lens?</h3>
- If x is the distance of nearest point of the defective eye and D is the least distance of distinct vision, then, the expression for focal length of the correcting lens will be,

- It is given that, the woman whose near point is 50cm from her eyes, assuming the least distance of distinct vision for a normal eye is 25cm. Thus, the focal length will be,

Thus, we can conclude that, the focal length of a lens needed by a woman whose near point is 50cm from her eyes is 50cm.
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Answer:
Explanation:
a )
According to graph the object moves with constant velocity of 10 m /s during first 8 s and then its velocity changes to - 5 m /s from 8 th second upto 12 th second .
Initial displacement = 8 m
displacement during 8 s = velocity x time
= 8 x 10 = 80 m
total displacement = 88 m
b )
displacement during period from 8 th to 12 th s
= - 5 x 4 = - 20 m
total displacement after 12 s
= 88 - 20 = 68 m
c ) average speed = total distance covered during 12 s / total time
= (80 + 20) / 12
= 8.33 m /s
average velocity = total displacement during 12 s / total time
= 80 - 20 / 12
= 60 / 12
= 5 m /s .