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Ivory Colliding Balls
Apparatus to demonstrate the conservation of momentum by the collision of balls having very hard surfaces is common, and ivory was a common material for the balls in the nineteenth century and early twentieth century. The use of ivory is not permitted now, and steel is the most common material for the balls. The balls on this apparatus are ivory.
Atwood's Machine
Atwood's machine is a device to observe the acceleration of a moving system acted upon by small forces. Two unequal masses are hung over a pulley by a light cord. The pulley turns with low friction, and the acceleration of the system of masses can be measured. The mass accelerated is the sum of the two masses on the string, and the force producing acceleration is the difference in the weights of those two masses. In this device, the pulley carrying the cord turns on roller bearings, like those designed by Atwood in the 17th century.
The second image shows the low-friction roller bearings
Goodnow Hall
Located on the Grinnell College campus and constructed in 1885, Goodnow Hall was the first building constructed after the devasting tornado of 1882. Goodnow was built with quartzite rock, at the time a rare material. The architect was Stephen C. Earle; E.A. Goodnow provided the $10,000 required for the construction.
Initially designed as a library and observatory, it became the home of the physics and mathematics departments following the construction of the Carnegie library in 1904. A wooden cornice from the original library is on display in the Physics Museum
The dome on the tower of Goodnow housed the Hsieh telescope, an Alvan Clark eight-inch refracting instrument. Two precision Seth Thomas clocks, one set on sideral time and the second on solar time, in conjunction with a Fauth transit telescope, a Fauth chronograph, provided accurate timekeeping. The eight-inch objective lens on display in the museum is the only remaining remnant of the telescope.
The small transit hut with the slotted roof beside Goodnow contained the transit telescope with telegraph connections to the Goodnow clock room with its two precision clocks and chronograph. All are on display in the museum. The Warner-Swasey filar micrometer used with the Hsieh telescope is also displayed in the museum.
In 1926 leakage problems forced the removal of the tower observatory dome and astronomy disappeared from Grinnell's curriculum until the 1960's. The current Grant O. Gale observatory with its 24-inch telescope was dedicated in 1984.
After the physics department moved to the new Science Building, Goodhow housed the psychology department from 1954 until 1988. Following a major restoration project in xxx which included replacing the limestone belts on the tower, the anthropology department moved to Goodnow. In 2019 after the anthropology department moved to the new Humanities and Social Sciences Center, Goodnow awaits its next occupant.
