Name: Modulus of Elasticity
Uploaded: 2019-07-19
Duration: 8 min 54 s
Description: Why are most long bridges made of steel? Can we replace it with another material? Learn about the types of elastic modulus and use them to know the strength...

Question

Steel is more elastic than rubber. Explain why?

Accepted Answer

The property of a body, by virtue of which it tends to regain its original size and shape when the applied force is removed, is known as elasticity. In other words, it is the property of a material to oppose the deformation caused to it. Young's modulus of the material determines the elasticity of the material.

Consider two wires, one of steel & another of rubber of equal length $L$ and of an equal area of cross-section $A$ . On applying equal force $F$ , on these wires, let $l_{s}$ and $l_{r}$ be the increase of the length of the steel wire and rubber wire respectively.

Young’s modulus for steel $Y_{s} = \frac{F . L}{A l_{s}} . . . (1)$

Young’s modulus for rubber $Y_{r} = \frac{F . L}{A l_{r}} . . . (2)$

On dividing equation one by second, we get

$\frac{Y_{s}}{Y_{r}} = \frac{l_{r}}{l_{s}} . . . (3)$

If the same force is applied to the wire of steel and rubber thread, which are of equal length and cross-section area, we will find that the extension in the rubber thread is much greater than extension in steel wire. Therefore, for a given stress, the strain produced in steel is much smaller than that produced in the rubber i.e. $l_{r} > l_{s}$ .

From equation $(3)$ ,

$Y_{s} > Y_{r}$

Young’s modulus for steel is greater than that for rubber. Therefore, steel is more elastic than rubber.

Steel is more elastic than rubber. Explain why?

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