Section III, 1920 [27] Trans. R.S.C. 



The Pendulum, Simple Harmonic Motion, The Elastic Moduli and 

 Impact — A Laboratory Experiment 



By John Satterly, F.R.S.C. 



(Read May Meeting, 1920) 



The author uses in the elementary Physics Laboratory at Toronto, 

 an experirnent which bears the name of "The Suspended Ball." The 

 main part of the apparatus is a heavy spherical iron ball which hangs 

 by a fine steel wire from the ceiling. The experiment is used as a 

 review experiment, for it comprises in itself experiments on : 



1. The triangle of forces; 



2. Simple harmonic motion; 



3. The simple pendulum; 



4. Young's modulus of the metal of the suspension wire; 



5. The modulus of rigidity of the metal of the suspension wire; 



6. The transverse vibration of wires; 



7. The longitudinal vibration of wires; 



and, provided that two balls hang side by side, experiments on: 



8. Impact and the Conservation of Momentum; 



9. The co-efficient of restitution. 



The iron ball E (Fig. 1), which weighs about 30 pounds, has been 

 trimmed to the spherical shape, and two hooks, H and K, fixed to it. 

 To one, H, is soldered the suspension wire, which is of such length that 

 with the upper end of the wire soldered to a metal frame screwed to 

 the ceiling the ball hangs with its bottom about an inch above the 

 bench. 



The other hook, K, is used as an attachment by which the ball 

 can be drawn to one side by a horizontal force. The first part of the 

 experiment consists in finding the relation between this horizontal 

 force and the horizontal displacement. To get several values of the 

 force, a chain, C, made up of 3 inch portions of a light chain (the 

 chain used to pull down blinds is convenient for the purpose), the 

 portions being joined together by ^-inch rings, Ri, R2, R3, etc. This 

 chain is linked up to a spring balance, D, reading to ounces. An old 

 wooden retort or burette stand, P, cut down to about 8 inches high, 

 is screwed to the bench in the line of movement of the ball. On 

 hitching the spring balance into the hook K, and looping in turn 

 successive rings over the post P, the ball can be pulled aside by differ- 

 ent amounts and the forces read off on the spring balance. To measure 

 the displacements an inch scale SS (reading to 1/10 in.) is screwed down 



