Lab Report

Using Gravitational Force as a Measurement Tool

Answer the following questions about the results of this activity. Record your answers in the boxes.

Send your completed lab report to your instructor. Don’t forget to save your lab report to your computer!

Activity 1

Record your data from Activity 1 in the boxes below. Enter the data for the sample you used in each trial (5000 rpm, 10000 rpm, etc…) in the appropriate columns and the corresponding g-force, number of layers, and position of layers position results.

You will need to use the following formula to assist with your laboratory report:

·  G-force =0 00001118 x radius of centrifuge arm x (rpm)2

·  The radius of the centrifuge arm for this instrument is 10 cm.

Speed / 5000 rpm / 10000 rpm / 15000 rpm / 20000 rpm
G-force
Number of Layers
Position of Layers
1.  Explain what happens to the G-force as the speed of the centrifuge increases.
2.  Which is likely the best speed to separate the components of this soil sample? Why?
3.  Describe in which layers you are likely to find the organic matter, gravel, sand, silt, and clay at the following speeds:
a.  5000 rpm
b.  15000 rpm

Activity 2

Record your data from Activity 2 in the boxes below. Enter the data for the sample you used in each trial (0.5, 1.5, 2.0, and 2.5 grams/ liter cesium chloride) in the appropriate columns with the corresponding g-force, number of layers, and position of layers results.

Cesium Chloride
grams/liter / 0.5 / 1.5 / 2.0 / 2.5
Number of Layers
Position of Layers
4.  Explain what happens to the drag as the cesium chloride concentration increases.
5.  Which is likely the best cesium chloride concentration to separate the components of this soil sample? Why?
6.  Describe in which layers you are likely to find the organic matter, gravel, sand, silt, and clay at the following speeds:
a.  0.5 grams/liter of cesium chloride
b.  2.5 grams/liter of cesium chloride
7.  Explain any differences in the thickness of similar bands at the different cesium chloride concentrations.
8.  Based on the data from Activities 1 and 2, which is likely the best speed and cesium chloride concentration combination to distinguish different types of soils? Why?