Final answer:
The plumb line in measurement is used to determine the verticality of an object or structure. It helps ensure that walls, columns, or other constructions are perfectly vertical. The force of gravity is relied upon to create a true vertical line.
Step-by-step explanation:
In measurement, the plumb line has the sole purpose of determining the verticality of an object or structure. It is a weighted string or line with a weight at one end and is used to create a vertical reference line.
For example, in construction or surveying, a plumb line is used to ensure that walls or columns are perfectly vertical. It can also be used to determine the depth of a well or the straightness of a ship's mast.
The plumb line relies on the force of gravity to create a true vertical line, making it an essential tool in accurate measurement.