# Can anyone help me with stoke's law for as-level physics? Thank you

edexcel exam board, maybe some worked though examples, or a link to helpful information! anything is appreciated

Posted Sat 5th January, 2013 @ 16:21 by Dyslexic_96

Hi firstly you can find loads of information on stoke's law in my resources. Just select anything called materials and you should find what you are looking for.

Stokes law is basically an equation for which you can work out the force of visous drag for a spherical object. The force of viscous drag is the force due to the visocity of a fluid. The equation is:

F = 6πrην

where π is pi, r is radius, η is the co-efficient of viscosity and v is velocity.

Now you can only work it out once the object has reached terminal velocity, otherwise the viscous drag (F) will be changing. The coefficient of viscosity if just a figure that will be given to you in exams when you need to us this equation. Occassionally you will be asked to work out the coefficient of viscosity or the terminal velocity. But in these cases just re-arrange the equation. All other values will be given to you.

So

η = F / 6πrν

v = F / 6πrη

There is only really one trick that exams can use when using this equation and that is they give you the diameter of the spherical object instead of the the radius. However as long as you read the question properly you should have no problem simply dividing it by 2. Just make sure you have the radius before you do calculations.

Answered Sat 5th January, 2013 @ 18:22 by Tilly - Team GR

Tilly, which exam board do you do for your AS subjects?

Answered Sat 5th January, 2013 @ 19:28 by Joanne

Physics - Edexcel

Chemistry - Edexcel

Biology - AQA

Extended project - Edexcel

Answered Sat 5th January, 2013 @ 19:29 by Tilly - Team GR

Oh okay, what career do you want to do by the way?

Answered Sat 5th January, 2013 @ 19:33 by Joanne

I'm not too sure yet - probably an astrogeologist. What about you?

Answered Sat 5th January, 2013 @ 19:55 by Tilly - Team GR
Edited by Tilly - Team GR on Sat 5th January, 2013 @ 19:55

No problem - a vet hopefully :) so what do you do an as astrogeologist?

Answered Mon 7th January, 2013 @ 19:08 by Joanne

Because I love space and astronomy, but I'm also really interested in geology, so it all fits together nicely into my perfect job.

Answered Mon 7th January, 2013 @ 21:30 by Tilly - Team GR

Nice :)

Answered Mon 7th January, 2013 @ 22:08 by Joanne