Upthrust, also known as buoyancy, is the upward force exerted by a fluid on an object immersed in it. It is a result of the difference in pressure between the top and bottom of the object.
Upthrust is important because it plays a significant role in the stability and equilibrium of an object in a fluid. It affects the weight and density of the object, and therefore, determines the conditions for independence on depth.
The two conditions for independence on depth are when the upthrust on an object is equal to its weight, and when the center of gravity of the object is below its center of buoyancy. These conditions ensure that the object will remain stable and not sink or float.
The density of an object determines the amount of upthrust it experiences. Objects with lower density than the fluid they are immersed in will experience more upthrust and therefore float, while objects with higher density will experience less upthrust and sink.
No, upthrust cannot be negative. It is always an upward force, and even if it is less than the weight of the object, it will still be considered a positive value. Negative upthrust would imply that the fluid is pushing the object downwards, which is not possible.