Blackwood ballistic pendulum
Date: 1940-1950
Inventory Number: 1998-1-0036
Classification: Ballistic Pendulum
Subject:
Maker: Central Scientific Company (1889 - 2000)
Cultural Region:
Place of Origin:
Dimensions:
48 x 57.5 x 12.5 cm (18 7/8 x 22 5/8 x 4 15/16 in.)
Accessories: data card (in instrument's file); brass sphere
Bibliography:
General Catalog of Laboratory Apparatus and Scientific Instruments
DescriptionThe pendulum consists of a cylindrical bob suspended by a strong light rod supported at its upper end by hardened steel cone pivot bearings. The pendulum support is a rigid bracket mounted upon the end of a strong steel rod fastened in the iron base. The pendulum bob is hollowed out to receive the projectile, a brass sphere (inside). A brass spring is inserted in this cavity in such a way as to catch and hold the brass ball firmly in the cylindrical bob in such a position that its center of gravity lies in the axis of the pendulum suspension rod. The pendulum hangs freely in the same position whether it contains the ball or not. The ball is drilled for mounting on the end of the propelling rod.
The projecting apparatus consists of a spring-actuated gun securely mounted at one end of the iron base. The propelling rod is turned down at the end to receive the brass ball. Upon the middle of the rod is mounted a collar which serves to engage the trigger and also to limit the motion of the rod when the gun is fired. The gun is fired by the pressure of the finger on the trigger when the handle is firmly grasped in the usual way.
In use, the projectile is fired into the bob, causing the pendulum to swing upward. It is caught at its highest point by a pawl which engages a tooth in the cruved rack. The surface of this rack lies on the arc of a circle whose center lies in the axis of suspension of the pendulum. A scale along the outer edge of the rack enables the operator to record the position of the pendulum.
[Description taken from the CENCO catalogue.] Original price in 1941: $45.00
The projecting apparatus consists of a spring-actuated gun securely mounted at one end of the iron base. The propelling rod is turned down at the end to receive the brass ball. Upon the middle of the rod is mounted a collar which serves to engage the trigger and also to limit the motion of the rod when the gun is fired. The gun is fired by the pressure of the finger on the trigger when the handle is firmly grasped in the usual way.
In use, the projectile is fired into the bob, causing the pendulum to swing upward. It is caught at its highest point by a pawl which engages a tooth in the cruved rack. The surface of this rack lies on the arc of a circle whose center lies in the axis of suspension of the pendulum. A scale along the outer edge of the rack enables the operator to record the position of the pendulum.
[Description taken from the CENCO catalogue.] Original price in 1941: $45.00
Signedon plaque: CENTRAL SCIENTIFIC CO.
FunctionAccording to the CENCO catalogue: "[This instrument] is for the study of the conservation of momentum. This apparatus was devised by Professor O. Blackwood of the University of Pittsburgh for use in his classes. The original design has been modified to satisfy the requirements of correct mechanical design, convenience of manupulation in the hands of students of various types, and of ruggedness.
The Blackwood Ballistic Pendulum presents in simplified form means for the study of the energy relationships growing out of Newton's second law of motion, yet its use involves an understanding of underlying theory of a kind to intrigue the most capable workers. Professor Balckwood incorporated in the design certain features which will catch the student's attention and hold his interest. Economy of production has been kept constantly in mind throughout the work of modifying the design of the apparatus. These characteristics of the apparatus are such, we believe, as to commend it to the large group of teachers of college physics who have long recognized the need for a simple means for presenting these relationships to the less advanced students."
The Blackwood Ballistic Pendulum presents in simplified form means for the study of the energy relationships growing out of Newton's second law of motion, yet its use involves an understanding of underlying theory of a kind to intrigue the most capable workers. Professor Balckwood incorporated in the design certain features which will catch the student's attention and hold his interest. Economy of production has been kept constantly in mind throughout the work of modifying the design of the apparatus. These characteristics of the apparatus are such, we believe, as to commend it to the large group of teachers of college physics who have long recognized the need for a simple means for presenting these relationships to the less advanced students."
Primary SourcesCentral Scientific Company, General Catalog of Laboratory Apparatus and Scientific Instruments [J-141] (Chicago: Central Scientific Company Laboratory Supplies, 1941), 1095, no. 75425.