Question

When a body is immersed in a fluid, it undergoes an apparent loss in weight. Why?

Answer 1

It’s because of upthrust (also called buoyant force). According to the Archimedes' principle, any object, partially or fully immersed in a fluid, experiences an upthrust equal to the weight of the fluid displaced by the object. And the apparent weight is given by $W_{apparent}=W_{actual}-Upthrust$.