Computer Intensive Physics
Day 6

Physics 211

Spring, 1998
January 29, 1998

Create a Word file with the file name MBL-6_{your team names}

Equipment:

Motion detector, coffee filters

The system is arranged with the motion detector mounted high above the floor of
the classroom. Remember the motion detector does not give good data for objects
closer than about 50 centimeters from the detector.

1) ( 3 pts)(a) Draw a complete free body diagram of a coffee filter as it falls through
the air near the surface of the earth and label all of the forces acting on it.

(b) What are the sources of the forces acting on the falling coffee filter?

(c) Using Newton's Second Law to solve for the acceleration of the coffee filter in
symbolic form in terms of the forces acting on the falling coffee filter. Solve
this equation for the situation when the falling filter reaches its terminal
velocity. {What does this mean about its acceleration? About the sum of the
forces acting on the falling filter?}

2) (3 pts)Derive an expression that enables you to determine how the drag force, or
air resistance,on a falling coffee filter might change with the velocity of the
falling filter by changing the mass of the falling filter.

Hint: assume that the drag force is proportional to some power, m, of the
velocity, soF= -k*v^m
drag^{where m is any real number.}

Also assume that you change the mass of the falling filters by stacking additional filters inside the first one, so the falling filters have a total mass that is an integer value, n, times the mass of one filter, so M = n*mfilterwhere n is an integer andmis the mass of one filter.filter Show your derivation, step by step, with explanations.

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