What is the definition of unit weight?

Unit weight is defined as the density of a material multiplied by the acceleration due to gravity. This definition captures the relationship between mass, volume, and the gravitational force acting on it. Essentially, unit weight provides a measure of how much weight is present in a specific volume of a substance.

To break it down further, density is the mass per unit volume, and when we multiply density by the gravitational acceleration (approximately 9.81 m/s² on Earth), we obtain the unit weight, which is typically expressed in terms like pounds per cubic foot or newtons per cubic meter. This concept is vital in various fields of engineering and physics, particularly in fluid mechanics and materials science, as it helps in assessing the behavior of materials under different forces and conditions.

The other choices do not accurately define unit weight. The weight of a particular volume of fluid does not account for the gravitational factor tied into the overall definition. The resistance of an object in fluid refers to drag rather than weight-related properties. The force exerted by an object due to gravity is a broader concept that pertains to weight in general but does not directly address the relationship between density and gravity that specifies unit weight.