Q.2.1: Determine the centre of mass for a body that lies above the plane z = 4 and below the sphere x² + y² + z² = 25. The density is constant with a value of k kg/m³. F(x, y, z) = -xi - yj + z³k.
Q.2.2: Where the surface S is described as the surface of the cone z = 2 + y between z = 1 and z = 3. Orientated downwards.
Please note that there are no mathematical errors or errors related to the square root symbol in the provided texts.