Home | Action Research Kit| Sample Problems | Resources | Product Information | |

Problems Sorted by Type | Problems Sorted by Subject | Problems Sorted by Chapter in UP |

** **
In this problem, you will derive an explicit form of Newton's drag law for air resistance whose structure we derived in a previous problem by dimensional analysis. The derivation below will provide the dimensionless coefficient that we were unable to find by dimensional analysis.

(b) Suppose the moving wall is a disk of radius *R* moving at a velocity *v* in a direction perpendicular to the plane of the disk. If there are *N* small particles per unit volume in the region of space the disk is sweeping through, how many of them will it encounter in a small time D*t*?

(c) Calculate the total momentum transferred to the air in the time D*t* by the disk assuming that there are *N* air particles per unit volume and they each have mass *m*.

(d) Find the force the disk exerts on the air and the force the air exerts on the disk. How do you know?

(e) Show that the force you calculated has the form

Not finding what you wanted? Check the Site Map for more information.

Page last modified October 15, 2002: D30