A smooth plane of pine 72" × 11" carries a loaded
slide of pine 9" × 9"; one end of the plane is
gradually elevated until the slide starts off.
+-----------+-------------+-----------+-----------+-----------+
| Number of |Total load on| Angle of | Angle of |Mean values|
|Experiment.| the slide |elevation. |elevation. | of the |
| | in lbs. |1st Series.|2nd Series.| angles. |
+-----------+-------------+-----------+-----------+-----------+
| 1 | 14 | 19°·5 | —— | 19°·5 |
| 2 | 56 | 20°·1 | 17°·2 | 18°·6 |
| 3 | 112 | 20°·3 | 18°·9 | 19°·6 |
+-----------+-------------+-----------+-----------+-----------+
145. We might, however, proceed differently in determining the angle of
friction, by giving the load a start, and ascertaining if the motion
will continue. To do so requires the aid of an assistant, who will
start the load with the help of the screw, while the elevation of the
plane is being slowly increased. The result of these experiments is
given in Table VIII.