Physics Elasticity Question 150
Question: The length of an elastic string is a metre when the longitudinal tension is 4 N and b metre when the longitudinal tension is 5 N. The length of the string in metre when the longitudinal tension is 9 N is
[EAMCET 2001]
Options:
A) $ a-b $
B) $ 5b-4a $
C) $ 2b-\frac{1}{4}a $
D)$ 4a-3b $
Show Answer
Answer:
Correct Answer: B
Solution:
Let L is the original length of the wire and K is force constant of wire. Final length = initial length + elongation $ L’=L+\frac{F}{K} $ For first condition $ a=L+\frac{4}{K} $ ?(i) For second condition $ b=L+\frac{5}{K} $ ?(ii) By solving (i) and (ii) equation we get $ L=5a-4b $ and $ K=\frac{1}{b-a} $ Now when the longitudinal tension is 9N, length of the string = $ L+\frac{9}{K} $ = $ 5a-4b+9(b-a) $
$ x=5b-4a $ .
BETA
