The buoyant force acting on a floating object is equal to its weight. This conclusion is supported by the principle of buoyancy, which states that an object will float when the upward buoyant force equals the downward gravitational force (weight). The discussion emphasizes the importance of understanding units and dimensionality in physics, particularly when differentiating between mass, density, and weight. Participants also highlight that a completely submerged object displaces a volume of liquid equal to its weight, reinforcing the relationship between buoyancy and weight.
PREREQUISITESStudents studying physics, educators teaching fluid mechanics, and anyone interested in understanding the principles of buoyancy and its applications in real-world situations.
Well, which of those possible answers has the same units as buoyant force? (That's Bystander's tip!)lucynemes86 said:I got no units. Nothing. Just wondering when an object floats, is it because the buoyant force is equal to its mass, specific gravity, density or weight?
Doc Al said:Well, which of those possible answers has the same units as buoyant force? (That's Bystander's tip!)
Right.lucynemes86 said:Weight? (Newton)
Thanks. I'm just new to physics. I had physics in high school over a decade ago but I don't remember much, even though I did well. I'm taking a class in college now (getting another degree) and I'm just having trouble with simple questions! :/Doc Al said:Right.
But it sounds like you need to learn more about buoyant force. This particular question can be answered without knowing anything (except units), since only one of the choices is even a force. But they won't all be like that.
Doc Al said:Right.
But it sounds like you need to learn more about buoyant force. This particular question can be answered without knowing anything (except units), since only one of the choices is even a force. But they won't all be like that.
Are you asking if the weight of the liquid displaced equals the weight of the object? Not in general.lucynemes86 said:Also, a completely submerged body displaces a volume of liquid equal to its weight too, right?
I think ByStander meant dimensionality, not units. If you know the units that will tell you the dimensionality, but not the other way around.lucynemes86 said:I got no units. Nothing. Just wondering when an object floats, is it because the buoyant force is equal to its mass, specific gravity, density or weight?
Think of a large Styrofoam beach ball. It would displace an amount of water that was quite heavy. Is the beach ball that heavy?lucynemes86 said:Also, a completely submerged body displaces a volume of liquid equal to its weight too, right?
Only if the only other force acting on the body is gravity, i.e. it is floating with neutral buoyancy.lucynemes86 said:Also, a completely submerged body displaces a volume of liquid equal to its weight too, right?
Right, not quite heavy... So, it displaces a volume of liquid equal to its density or buoyant force? Maybe to its own volume?phinds said:Think of a large Styrofoam beach ball. It would displace an amount of water that was quite heavy. Is the beach ball that heavy?
Thank you!haruspex said:Only if the only other force acting on the body is gravity, i.e. it is floating with neutral buoyancy.
Otherwise, all you can say is that it displaces its own volume.
If it is tethered to the bottom then the buoyant force is also having to balance the tension in the tether.
If it is resting on the bottom then the buoyant force is assisted by the normal force.
Which one do you think? How could it be density? Do you understand the use of units in figuring out this kind of thing?lucynemes86 said:Right, not quite heavy... So, it displaces a volume of liquid equal to its density or buoyant force? Maybe to its own volume?
But note that was for a completely submerged body. A floating ball of styrofoam will not be completely submerged. What will the displaced volume correspond to in this case?lucynemes86 said:Thank you!
Volume. Sorry. I'm not a genius. Had physics over a decade ago and don't remember much.phinds said:Which one do you think? How could it be density? Do you understand the use of units in figuring out this kind of thing?
OK, well you didn't answer my question about units so let me be specific. NEVER give an answer to a physics question unless you are confident that you have the units right. That catches LOTS of the mistakes that we all make when we are starting out.lucynemes86 said:Volume. Sorry. I'm not a genius. Had physics over a decade ago and don't remember much.
Thanks again...haruspex said:But note that was for a completely submerged body. A floating ball of styrofoam will not be completely submerged. What will the displaced volume correspond to in this case?
One of your answers in post #14 was sort of correct, that the weight of the water displaced is equal to the buoyant force, but that is true whether the object is floating, resting on the bottom, or tethered. In the specific case of a floating body, what other force is the buoyant force equal to?
Right.lucynemes86 said:In case of a floating object buoyant force equals weight right?
Yes.lucynemes86 said:Thanks again...
In case of a floating object buoyant force equals weight right?