# A Load of 10 Kg is Suspended by a Metal Wire 3 M Long and Having a Cross-sectional Area 4 Mm2. Find(A) the Stress(B) the Strain and (C) the Elongation. Young Modulus of the Metal is 2.0 × 1011 N M−2. - Physics

Short Note

A load of 10 kg is suspended by a metal wire 3 m long and having a cross-sectional area 4 mm2. Find (a) the stress (b) the strain and (c) the elongation. Young modulus of the metal is 2.0 × 1011 N m−2

#### Solution

Given:
Mass of the load (m) = 10 kg
Length of wire (L) = 3 m
Area of cross-section of the wire (A) = 4 mm2 = 4.0 × 10−6 m2
Young's modulus of the metal Y = 2.0 × 1011 N m−2

(a) Stress = F/A

F = mg
=  $10 \times 10$ = 100 N    (g = 10 m/s2)

$\therefore \frac{F}{A} = \frac{100}{4 \times {10}^{- 6}}$
$= 2 . 5 \times {10}^7 \text{ N/ m }^2$

(b) Strain = $\frac{\Delta L}{L}$

Or,

$\text{ Strain } = \frac{\text{ Stress }}{Y}$

$\text{ Strain }= \frac{2 . 5 \times {10}^7}{2 \times {10}^{11}}$
$= 1 . 25 \times {10}^{- 4} \text{ N/ m}^2$

(c) Let the elongation in the wire be $∆ L$ .

$\text { Strain} = \frac{\Delta L}{L}$
$\Rightarrow \Delta L = \left( \text{ Strain } \right) \times L$
$= 1 . 25 \times {10}^{- 4} \times 3$
$= 3 . 75 \times {10}^{- 4} \text{ m}$

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#### APPEARS IN

HC Verma Class 11, 12 Concepts of Physics 1
Chapter 14 Some Mechanical Properties of Matter
Q 1 | Page 300