1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Using airflow to find force

  1. Jan 12, 2015 #1

    I am doing an experiment where I am measuring the airflow readings (m/s) of different fans. I then was hoping to use this to work out the force and then from that the power to compare the efficiencies of the different fans. I was wondering if anyone had any suggestions for what equations to use to find the force from the air flow as I haven't found any that are particularly helpful?

  2. jcsd
  3. Jan 12, 2015 #2

    Doug Huffman

    User Avatar
    Gold Member

    Better. Suspend the fan as a simple pendulum and measure the displacement and weight just like in physics lab.
  4. Jan 14, 2015 #3


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Wikipedia appears to have an equation for thrust...

    Fx = ½ρ (CS2 - CU2)

    ρ = air density
    CS2 = velocity downstream of the fan
    CU2 = velocity upstream of the fan
  5. Feb 16, 2015 #4
    Look at Pitot & Bernoulli
  6. Feb 16, 2015 #5
    what do you mean by force of an airflow? it does not exist something like that.
    If u mean the thrust produced by the fan i quote pendulum approach! :p
  7. Feb 16, 2015 #6
    The power or force is equal to the change of momentum of the air. The efficiency is how much energy is being used to change the momentum.
    Measure accurately velocity in and out and the energy consumption of the fan.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook