Fluids, finding the density of a sphere in oil Please help

In summary, a small sphere with a diameter of 10 mm is falling at a constant velocity of 50 mm/s in SAEIOW oil at 200 degrees. The drag force on the sphere is 225N, calculated using the equation F = Cd/0.5 x rho x U^2 x A. However, there may be an error in the equation as using it to calculate the density of the sphere gives an incorrect answer.
  • #1
abs123456
15
1

Homework Statement



A small sphere (diameter = 10 mm) is left to fall in a fluid (oil, SAEIOW) at 200 degrees
with a constant velocity of 50 mm/s..

The Following data is available:
- For SAEIOW oil at 20 degrees: p = 920 kg/m3, μ = 0.1 Pa.s

a) The drag force on the sphere
b) The density of the sphere.



Homework Equations




Cd = 24/Re^0.645

The Attempt at a Solution



a) I managed to do the first part, by using Cs in the equation F= Cd/0.5 x rho x U^2 x A

And i got 225N..

b) However i am not too sure about doing part b... if i equate the drag force to the weight it gives me
the wrong answer for density.. This part is a 13 mark question too..
 
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  • #2
I think you have an error in the drag force equation.
F = Cd * 0.5 * rho * A * U^2
 

FAQ: Fluids, finding the density of a sphere in oil Please help

What is the definition of density?

Density is a measure of the mass of a substance per unit volume. It is commonly expressed in units of grams per cubic centimeter (g/cm3) or kilograms per cubic meter (kg/m3).

How is density related to the buoyancy of an object?

Density is directly related to the buoyancy of an object. If the density of an object is greater than the density of the fluid it is placed in, it will sink. If the density of an object is less than the density of the fluid, it will float.

How do you find the density of a sphere in oil?

To find the density of a sphere in oil, you will need to know the mass and volume of the sphere. First, measure the mass of the sphere using a scale. Then, measure the volume of the sphere by submerging it in the oil and recording the change in volume. Finally, divide the mass by the volume to find the density.

Can the density of a sphere in oil change?

Yes, the density of a sphere in oil can change. This can occur if the temperature of the oil changes, causing the volume of the oil to expand or contract. It can also change if the sphere absorbs or releases oil, altering its mass.

What factors can affect the accuracy of the density measurement?

The accuracy of the density measurement can be affected by various factors, such as experimental errors, temperature changes, and the purity of the oil. It is important to calibrate all equipment and use high-quality materials to obtain the most accurate measurement possible.

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