Static fluids; Density; Buoyancy

In summary, the density of the toy dinosaur is 900 kg/m^3 and it is partially submerged with 90% of its volume underwater. After a layer of oil with a density of 869 kg/m^3 is added on top of the water, the percentage of the dinosaur submerged in the water can be calculated using the principle that the dinosaur is suspended at rest with x% of its volume in the water and (1-x)% of its volume in the oil. The hint suggests using x to calculate the percentage, while keeping in mind that the dinosaur is still floating and is lighter than the water but heavier than the oil.
  • #1
awertag
64
0

Homework Statement



A toy dinosaur floats on water in a container and is partially submerged with 90 % of its volume underwater (submerged).

(a) What is the density of the dinosaur?
I got this answer right. It is 900 kg/m^3

A layer of oil, with a density of 869 kg/m3, is now poured into the container on top of the water to a depth that more than covers the dinosaur.

Find the percentage of the dinosaur submerged in the water after the oil was added. (Ignore the buoyancy of the air before the oil is added.)

This answer I did not get right, and I really don't know how to do it.(Hint: the dinosaur is suspended at rest in the fluids with x% of its volume in the water and (1-x)% of its volume in the oil

Homework Equations


The Attempt at a Solution

i tried 900 ÷ 869 and that gives 1.03567 then i thought to subtract that from 100 percent. I know that doesn't make much sense, but I was grasping for any kind of path that might get me the answer. (sound desperate enough to you?) lol help is very much appreciated!
 
Last edited:
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  • #2
hi awertag! :smile:
awertag said:
Hint: the dinosaur is suspended at rest in the fluids with x% of its volume in the water and (1-x)% of its volume in the oil

what happened to x ?? :confused:

follow the hint! …

what principle is involved? use x to calculate it! :smile:

(and remember that the dinosaur is still floating … it's lighter than the water but heavier than the oil)
 

Related to Static fluids; Density; Buoyancy

1. What is the definition of a static fluid?

A static fluid is a fluid that is not moving or has a constant velocity. This means that there is no net force acting on the fluid and it is in a state of equilibrium.

2. How is density defined and measured in relation to fluids?

Density is defined as the mass of a substance per unit volume. In the case of fluids, density is typically measured in units of kilograms per cubic meter (kg/m^3). It can be measured using various instruments such as a hydrometer or a density meter.

3. What is buoyancy and how does it relate to fluid density?

Buoyancy is the upward force exerted on an object submerged in a fluid. It is directly related to the density of the fluid, as denser fluids exert a greater buoyant force on objects. This is why objects that are less dense than water, such as wood or plastic, float on the surface while denser objects, like rocks, sink.

4. What is Archimedes' principle and how does it apply to buoyancy?

Archimedes' principle states that the buoyant force on an object submerged in a fluid is equal to the weight of the fluid displaced by the object. In other words, the buoyant force is equal to the weight of the fluid that the object "pushes out of the way" when it is submerged. This principle helps explain why objects with different densities will have different levels of buoyancy in a fluid.

5. How can you calculate the buoyant force on an object in a fluid?

The buoyant force can be calculated using the formula Fb = ρVg, where ρ is the density of the fluid, V is the volume of the displaced fluid, and g is the acceleration due to gravity. This formula can be used to determine the buoyant force on an object, and if the object's weight is less than the buoyant force, it will float. If the object's weight is greater than the buoyant force, it will sink.

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