What is the term for the upward force that acts on an object in a fluid?

The upward force that acts on an object in a fluid is known as upthrust, often referred to in this context as buoyant force. This force arises due to pressure differences in the fluid; the pressure at the bottom of an object submerged in a fluid is greater than the pressure at the top, resulting in a net upward force. This concept is described by Archimedes’ principle, which states that the buoyant force is equal to the weight of the fluid displaced by the object.

While buoyancy is another term commonly used to describe this effect, it specifically emphasizes the object's ability to float or rise in a fluid due to upthrust. Both terms are interconnected, but in the context of the question focusing on the "upward force," upthrust is the more precise answer.

Understanding this force is essential in many applications, such as ship design, swimming, and even understanding how balloons rise in the atmosphere. Recognizing the role of upthrust allows us to predict the behavior of objects in various fluid environments.