After effects of elasticity are maximum for

For the tangential stress on the cross-section $PQRS$ to be maximum,$\theta = $ ....... $^o$

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 ......

What is a plastic body and plasticity?

Anvils made of single crystals of diamond,with the shape as shown in the figure,are used to investigate the behavior of materials under very high pressures. The flat faces at the narrow end of the anvil have a diameter of $0.50 \; mm$,and the wide ends are subjected to a compressional force of $50,000 \; N$. What is the pressure at the tip of the anvil?

The pointer reading versus load graph for a spring balance is as given in the figure. The spring constant is ........ $kg/cm$.