Homework Help: physics

Posted by anna on Wednesday, November 2, 2011 at 11:16pm.

water at 20°C has viscosity n=1.0*10^-3 Ns/m^2. sand grains have density 2400kg/m^3. suppose a 1.1 mm diameter sand grain is dropped into a 51m deep lake whose water is a constant 20°C. If the sand grain reaches terminal speed almost instantly (a quite good approximation), how long will it take the sand grain to settle to the bottom of the lake?

physics - drwls, Thursday, November 3, 2011 at 12:37am
Use Stokes' drag equation for the terminal velocity.

Stoke's equation says, for a sphere in a viscous fluid,
F=6(pi)RnVc,
where F is the force, R is the radius of the sphere, n is the viscosity, and V is the velocity through the fluid.
For the force F, use the weight minus the buoyancy force.

Divide the lake depth by that velocity.
physics - drwls, Thursday, November 3, 2011 at 12:38am
Make that last term V, not Vc
physics - Mustafa Qader, Tuesday, February 28, 2012 at 4:42pm
a) Vterm = (mg)/(6pi N R)

b)V term = ((4/3)pi R^3)pg))/(6pi N R)

Answer this Question

Related Questions

Chemistry - Why does sand tends to get hotter than water? I'm sure this isn...
please help idin't get it - 5.imagine you are at the beach on a very hot ...
science - 5.imagine you are at the beach on a very hot day. you walk toward the ...
science - 5.imagine you are at the beach on a very hot day. you walk toward the...
physics - Grains of fine California beach sand are approximately spheres with ...
Math- college - A company has to ship 1148 kg of sand,if one bag can hold 13kb ...
Science - Describe the method you would use to seperate eachg mixture. Methods: ...
math - container A has twice the capicity of container B. container A is full of...
math - container A has twice the capicity of container B. container A is full of...
math - container A has twice the capicity of container B. container A is full of...

For Further Reading

First Name:
School Subject:
Answer: