Linear Drag Force Homework: Acceleration & Constant Speed Calculations

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Homework Help Overview

The discussion revolves around a physics problem involving a ball sinking in a liquid, focusing on the concepts of acceleration due to gravity and drag force. The ball has a density of 1450 kg/m³, while the liquid has a density of 1400 kg/m³. Participants are exploring the acceleration of the ball when dropped and the constant speed at which it will sink, assuming linear drag.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the calculation of acceleration using a provided formula and question how to determine the constant sinking speed. There is mention of the need for the equation related to viscous drag force on a sphere, indicating a gap in knowledge regarding this concept.

Discussion Status

The discussion is ongoing, with some participants providing initial calculations for acceleration while others express uncertainty about the next steps for finding the constant speed. There is a suggestion to look up Stokes' Law, indicating a potential direction for further exploration.

Contextual Notes

Participants are working under the constraints of a homework assignment, which may limit the resources they can use or the methods they can apply. The discussion reflects varying levels of familiarity with the relevant equations and concepts.

antoman
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Homework Statement


We sink ball with density 1450 kg/m^3 in some liquid with density 1400 kg/m^3

a) What's acceleration in moment we drop the ball?
b) With what constant speed will the ball sink in balace? Assuming that the drag force is linear. Radius of ball is 3mm and viscosity of liquid is 200 Pa s.

Homework Equations



a=(g*(ρb-ρl))/ρb


The Attempt at a Solution


a... acceleration
ρb=1450 kg/m^3
ρl=1400 kg/m^3
g=9,81 m/s^2

a) That's easy, using the formula and you get a=0,338 m/s^2
b) Need help here, no idea how to solve
 
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antoman said:

Homework Statement


We sink ball with density 1450 kg/m^3 in some liquid with density 1400 kg/m^3

a) What's acceleration in moment we drop the ball?
b) With what constant speed will the ball sink in balace? Assuming that the drag force is linear. Radius of ball is 3mm and viscosity of liquid is 200 Pa s.

Homework Equations



a=(g*(ρb-ρl))/ρb


The Attempt at a Solution


a... acceleration
ρb=1450 kg/m^3
ρl=1400 kg/m^3
g=9,81 m/s^2

a) That's easy, using the formula and you get a=0,338 m/s^2
b) Need help here, no idea how to solve

Have you learned the equation for calculating the viscous drag force (in creeping flow) on a sphere of diameter, when the sphere is moving with a velocity v relative to the viscous fluid?
 
Chestermiller said:
Have you learned the equation for calculating the viscous drag force (in creeping flow) on a sphere of diameter, when the sphere is moving with a velocity v relative to the viscous fluid?

If you mean in colledge probably yes, but me personaly don't know that equation.
 
antoman said:
If you mean in colledge probably yes, but me personaly don't know that equation.

Google Stokes Law.
 

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