A wire elongates by l mm when a load W is hanged  from it. If the wire goes over a pulley and two weights W each are hung at the two ends, the elongation of the wire will be \left ( in\: mm \right )

  • Option 1)

    l/2

  • Option 2)

    l

  • Option 3)

    2l

  • Option 4)

    zero

 

Answers (1)

Aw we learnt in

Young Modulus -

Ratio of normal stress to longitudnal strain

it denoted by Y

Y= \frac{Normal \: stress}{longitudnal\: strain}

- wherein

Y=\frac{F/A}{\Delta l/L}

F -  applied force

A -  Area

\Delta l -  Change in lenght

l - original length

 

 

 

 

At equilibrium T = w

y=\frac{w/A}{L/L}                                                (i)

Now in case (ii)  T = w

\therefore\ y=\frac{w/A}{\frac{L/2}{L/2}}

\Rightarrow\ \; y=\frac{w/A}{l/L}

i.e. Elongation is the same. 

Correct option is 2.

 


Option 1)

l/2

This is an incorrect option.

Option 2)

l

This is the correct option.

Option 3)

2l

This is an incorrect option.

Option 4)

zero

This is an incorrect option.

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