Which pair of following statement is correct for orthogonal cutting using a single-point cutting tool?
$$P.$$ reduction in friction angle increases cutting force
$$Q.$$ Reduction in friction angle decreases cutting force
$$R.$$ Reduction in friction angle increases chip thickness
$$S.$$ Reduction in friction angle decreases chip thickness

Cutting tool is much harder than the work piece. Yet the tool wears out during the tool-work interaction, because

The diameter of a recessed ring was measured by using two spherical balls of diameter $${d_2} = 60mm$$ and $${d_1} = 40mm$$ as shown in the figure.

The distance $${H_2} = 35.55\,\,mm$$ and $${H_1} = 20.55\,\,mm$$. The diameter ($$D,$$ in $$mm$$) of the ring gauge is __________________.

The stress-strain curve for mild steel is shown in the figure given below. Choose the correct option referring to both figure and table