Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Need help for a lab due tommorow

  1. Apr 4, 2006 #1
    we had a experiment dropping paper baking cups from the ceiling to the ground.

    started off with 8 removing 1 each time till we had 1.

    The purpose of the lab is to determine the value of the shape factor value for empty baking cup.

    we are given the equation D=opAv(squared)
    We need to include (I need help trying to find):

    -Analysis of the equation to show how you intend to obtain a value for the shape factor (o)
    -the variables that you intend to measure and a description of how you will measure them
    -suggestions as to instrumental methods that could be employed in this experiment to obtain a more precise value for the shape factor

    any help is appreciated.
    Last edited: Apr 4, 2006
  2. jcsd
  3. Apr 5, 2006 #2


    User Avatar
    Homework Helper

    The drag, [itex]D[/itex], is directly proportional to [itex]v^2[/itex]. So graph of these will have a gradient of [itex]\frac{1}{2}CA\rho[/itex], where [itex]C[/itex] is the drag coefficient - which you intend determining -, [itex]A[/itex] the cross sectional area of the cup and [itex]\rho[/itex] is the density of air, all of which is constant during the experiment.

    So one need to determine the drag and velocity for the various falls with different amount of cups. When the cups fall they will eventually reach a constant speed - the terminal velocity [itex]v_T[/itex] - which you need to determine, at this point during the fall the drag will be equal to the weight of the cups at that stage.

    A graph of the weight of the cups versus the square of the terminal velocity will then give you what you want.
    Last edited: Apr 5, 2006
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook