Turn on thread page Beta
    • Thread Starter
    Offline

    0
    ReputationRep:
    What is the upthrust on a 1cm diameter steel ball in water?
    Density of steel = 8100kgm^-3
    Density of water = 1000kgm^-3

    if i were given the coefficient of viscosity id probably be able to work this out. any ideas?

    thanks in advance
    Offline

    1
    ReputationRep:
    Upthrust = Weight of Fluid Displaced
    Hence , mass of water displaced = density * volume = (1000) * (4/3 pi (1/100)^3)
    Hence weight displaced = mass * g = (1000) * (4/3 pi (1/100)^3) * 9.81 = Upthrust

    Coefficient of visc needed only for drag force....

    Upthrust + Drag = Weight of ball
    [at terminal velocity]
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by antonfigo)
    Upthrust = Weight of Fluid Displaced
    Hence , mass of water displaced = density * volume = (1000) * (4/3 pi (1/100)^3)
    Hence weight displaced = mass * g = (1000) * (4/3 pi (1/100)^3) * 9.81 = Upthrust

    Coefficient of visc needed only for drag force....

    Upthrust + Drag = Weight of ball
    [at terminal velocity]
    hmm the answer should be 5.1 x 10^-3.

    is anything supposed to be done with the steel density value?
    Offline

    1
    ReputationRep:
    5.1x10^-3 or 4.1x10^-3
    Remember to convert 1 cm to 1/100 m

    No...Steel density value is not needed for upthrust...but we need steel ball's volume which is equal to volume of water displaced...
    Offline

    10
    antonfigo has used 1cm in the calculation, but this is the diameter of the sphere. The formula requires the radius; half of this.
    Offline

    1
    ReputationRep:
    (Original post by Stonebridge)
    antonfigo has used 1cm in the calculation, but this is the diameter of the sphere. The formula requires the radius; half of this.
    Oh yea!
    I overlooked that :P ...now theres the real answer
    Offline

    0
    ReputationRep:
    1. Calculate the volume of the displaced liquid (volume of the block or object)
    2. Calculate the mass of the displaced liquid using the formula=density x volume
    3. Calculate the weight of the displaced liquid using the formula weight=massx10
    Always write it down in Newton or N in kilograms so if the answer is 1.0x20=20grams its 0.020 kg then you use the formula weight = massx10 so the answer is: 0.20N
    Offline

    10
    (Original post by Ripiramon)
    1. Calculate the volume of the displaced liquid (volume of the block or object)
    2. Calculate the mass of the displaced liquid using the formula=density x volume
    3. Calculate the weight of the displaced liquid using the formula weight=massx10
    Always write it down in Newton or N in kilograms so if the answer is 1.0x20=20grams its 0.020 kg then you use the formula weight = massx10 so the answer is: 0.20N
    Welcome to TSR physics.

    Thanks for this.

    This thread was started in 2010 and is now closed.
 
 
 
Turn on thread page Beta
Updated: January 21, 2015
The home of Results and Clearing

4,396

people online now

1,567,000

students helped last year

University open days

  1. Bournemouth University
    Clearing Open Day Undergraduate
    Fri, 17 Aug '18
  2. University of Bolton
    Undergraduate Open Day Undergraduate
    Fri, 17 Aug '18
  3. Bishop Grosseteste University
    All Courses Undergraduate
    Fri, 17 Aug '18
Poll
A-level students - how do you feel about your results?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.