3 replies to this topic

[pyro38]

Hi i am a Biology Student and its really giving me problems this one, can someone help?

"A string supports a solid iron object of mass 180g totally immersed in a liquid of density 800kgm-3. Calculate the tension of the string if the density of iron is 8000kgm-3"

I am confused here, Archimedes principle for immersed bodies states that downward force - upward force = net force , is net force tension? With these parameters is is possible to calculate the tension?

One of my assumptions on this is that the string weight is ignored.

JP

[Andree]

IMO tension is the force, ignoring the string weight T = m*g*[(ro_solid-ro_liquid)/ro_solid]

[djack77494]

I am confused here, Archimedes principle for immersed bodies states that downward force - upward force = net force , is net force tension? With these parameters is is possible to calculate the tension?

JP,
Ignoring the string's weight is very reasonable. Your string is obviously in tension. With no water present, it would support the full weight of the iron mass. Since the iron mass is submerged in a liquid, you must apply Archimedes' Principle as you considered. This principle will adjust the net weight of the iron mass by subtracting the buoyance force, which is due to the displacement of a volume of the liquid by the iron mass. The problem is fully solvable. Start with a free body diagram of the iron mass. Three forces act on it - gravity, the buoyant force, and tension in the string.

(Why did you ever go to a chemical engineering website with a physics problem?)

[pyro38]

(Why did you ever go to a chemical engineering website with a physics problem?)

This is one of the problems in my fluid flow course. Hence Chemical Engineering. Thanks for advice i managed to solve this.

JP