Q 1 :    

An elastic spring under tension of 3 N has a length a. Its length is b under tension 2 N. For its length (3a-2b), the value of tension will be ______ N.             [2024]



(5)     k(a-x0)=3a=3k+x0                ...(i)

          k(b-x0)=2b=2k+x0               ...(ii)

          Now, 3a-2b=9k+3x0-4k-2x0=5k+x0

          {(3a-2b)-x0}=5k

           k{(3a-2b)-x0}=5     T=5N

 



Q 2 :    

A massless spring gets elongated by amount x1 under a tension of 5 N. Its elongation is x2 under the tension of 7 N. For the elongation of (5x12x2), the tension in the spring will be,         [2025]

  • 15 N

     

  • 20 N

     

  • 11 N

     

  • 39 N

     

(3)

kx1=5 N  x1=5k

kx2=7 N  x2=7k

Then (5x12x2)k=5×52×7=11 N.



Q 3 :    

The length of a light string is 1.4 m when the tension on it is 5 N. If the tension increases to 7 N. the length of the string is 1.56 m. The original length of the string is ______ m.          [2025]



(1)

T=K(ll0)

 5=K(1.4l0)

 7=K(1.56l0)

 51.4l0=71.56l0

 l0=1 m