The breaking stress of a wire depends upon

Identify whether the following statements are True or False:
$(a)$ If a body breaks immediately after the elastic limit,then this body is known as ......
$(b)$ An elastic body which can be stretched to cause large strains is called ......

$A$ $50 \;kg$ girl wearing high heel shoes balances on a single heel. The heel is circular with a diameter $1.0 \;cm$. What is the pressure exerted by the heel on the horizontal floor?

If under an external force,a change in length $\Delta l$ occurs in a rod of original length $l$,then write the formula for longitudinal strain.

The elasticity of Invar:

The length of an elastic string is $a$ metres when the longitudinal tension is $4 \ N$ and $b$ metres when the longitudinal tension is $5 \ N$. The length of the string in metres when the longitudinal tension is $9 \ N$ is