Final answer:
In economics, capital is the factor of production that is generally fixed in the short run, while labor is considered a variable factor that can be adjusted.
Step-by-step explanation:
In economics, the resource that is generally fixed in the short run is capital. Capital refers to physical assets used in production, such as a factory building or machinery. These assets cannot be easily changed or adjusted in the short run, leading to their classification as fixed factors of production. On the other hand, labor, which refers to the work done by individuals, is generally considered a variable factor that can be adjusted in response to changes in production needs.