Q1: The pressure exerted by

ANS:D - All the above.

1. The pressure exerted by the sewage when running full from inside is called internal pressure: This refers to the force per unit area exerted by the sewage on the inner walls of the pipe when the pipe is filled with sewage. This pressure is generated due to the weight and flow dynamics of the sewage within the pipe.
2. The internal pressure, if any, causes tensile stress in the pipe material: When the internal pressure of the sewage exceeds the pipe's design limits or if the pipe is not properly supported, it can lead to tensile stress in the pipe material. Tensile stress is the stress that tends to pull the material apart, and it occurs when forces act to stretch an object.
3. Pressure sewers are designed to be safe in tension: Pressure sewer systems are engineered to withstand the internal pressure exerted by the sewage without experiencing failure due to tensile stress. This involves selecting appropriate pipe materials, ensuring proper installation techniques, and designing the system with safety factors to account for variations in operating conditions.