2. Questions Bank
  3. JEE Main & Advanced
  4. Physics
  5. Gravitation / गुरुत्वाकर्षण

JEE Main & Advanced Physics Gravitation / गुरुत्वाकर्षण Question Bank Mock Test - Gravitation and Mechanical Properties of Solid

  • question_answer
    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

    A) \[a-b\]  

    B) \[5b-4a\]

    C) \[2a-\frac{1}{4}a\]       

    D) \[4a-3b\]

    Correct Answer: B

    Solution :

    [b] Let L be the original length of the wire and K be the 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 equations (i) and (ii), we get \[L=5a-4b\] and \[K=\frac{1}{b-a}\] Now when the longitudinal tension is 9 N, length of the string \[=L+\frac{9}{K}=5a-4b+9(b-a)-5b-4a.\]


You need to login to perform this action.
You will be redirected in 3 sec spinner