Question

The stress-strain curves of three wires of different materials are shown in figure. $P, Q$ and $R$ are the elastic limits of the wires.

I. Elasticity of wire $P$ is minimum.
II. Elasticity of wire $Q$ is maximum.
III. Tensile strength of $R$ is maximum.
Which of the following statement(s) is/are correct?

• A. Only I
• B. Both I and III
• C. Only II
• D. None of these

Answer 1

Answer: (B)

In strain-stress curve, slope of curve $=\frac{1}{Y}$
From the given diagram we can write, $\frac{1}{Y_{P}}>\frac{1}{Y_{Q}}>\frac{1}{Y_{R}}$
Therefore, elasticity of $P$ or $Y_{P}$ is minimum and that of $R$ is maximum.
Elasticity of $Q$ lies between them (between $P$ and $R$ ).
As elasticity of $R$ is maximum, which means it can bear maximum stress, so its tensile strength is maximum.
So, statements I and III are correct but II is incorrect.