The longitudinal strain is only possible in

$A$ vertical hanging bar of length $l$ and mass $m$ per unit length carries a load of mass $M$ at its lower end. Its upper end is clamped to a rigid support. The tensile stress at a distance $x$ from the support is (where $A$ is the area of cross-section of the bar):

What is the shape of the graph of stress $\to$ strain up to the elastic limit?

$A$ force $F$ is needed to break a copper wire having radius $R$. The force needed to break a copper wire of radius $2R$ will be

$A$ tangential force of $100 \,N$ is applied on the top face of a cubic block of side $0.1 \,m$. If the top face is displaced by $0.02 \,cm$ relative to the bottom face,what is the tangential strain?

What is called a brittle material? What is called a ductile material?