The weight of a body on a support is determined by several factors, including the mass of the body, the gravitational force acting on the body, and the reaction force from the support.

The mass of the body refers to the amount of matter contained within the body. This is a constant value and does not change with the type of support the body is on.

The gravitational force is the force exerted on the body by the Earth's gravitational pull. This force is dependent on the mass of the body and the acceleration due to gravity, and is represented by the equation F = mg, where m is the mass of the body and g is the acceleration due to gravity.

The reaction force from the support is the force that the support exerts on the body in order to keep it in equilibrium. This force is equal in magnitude but opposite in direction to the gravitational force acting on the body, and is represented by the equation F_support = -mg.

Therefore, the weight of a body on a support is determined by the magnitude of the gravitational force acting on the body and is equal to the mass of the body multiplied by the acceleration due to gravity. In other words, the weight of a body on a support is directly proportional to the mass of the body.