Why is cooking faster in a pressure cooker?

The temperature of Bhakhra dam water at the ground level with respect to the temperature at a high level should be:

An iron rod of heat capacity $C$ is heated to temperature $8T_0$. It is then put in a cylindrical vessel of adiabatic walls having two moles of air which can be treated as a diatomic ideal gas at temperature $T_0$ and closed by a movable piston which is also adiabatic. The atmospheric pressure is $P_0$. The cylinder with the piston combined have a heat capacity $2C$. Find the equilibrium temperature. (Assume the temperature of air to be uniform and equal to the vessel at all times).

During summers in India,one of the common practices to keep cool is to make ice balls of crushed ice,dip them in flavoured sugar syrup,and sip them. For this,a stick is inserted into crushed ice,and it is squeezed in the palm to make it into a ball. Equivalently in winter,in those areas where it snows,people make snowballs and throw them around. Explain the formation of a ball out of crushed ice or snow in the light of the $p-T$ diagram of water.

Water falls from a height of $500 \ m$. What is the rise in temperature of water at the bottom if the whole energy remains in the water? (Assume $g = 9.8 \ m/s^2$ and specific heat capacity of water $c = 4200 \ J/kg \cdot ^\circ C$)

The heat required to change $1 \,kg$ of ice at $-8^{\circ} C$ into water at $20^{\circ} C$ at $1 \,atm$ of pressure is closest to .............$\,kJ$. (Assume that ice has a specific heat capacity $2.1 \,kJ / kg \cdot K$,water has a specific heat capacity $4.2 \,kJ / kg \cdot K$,and the latent heat of fusion of ice is $333 \,kJ / kg$.)