Atwood's Machine

Concept Overview

1. Determination of acceleration of each object and tension in the cord connecting them.
2. Application of Newton's 2nd Law.

Lecturer Procedure

Atwood's machine matches a mathematical example from the lecture.

Historical References; Taken from original work of Percy H. Carr, 1970 

“This machine was invented by George Atwood (1746-1807), an English physicist who described this device in ‘Treatise on Rectilinear Motion and Rotation of Bodies (1784).”
 

“If we assume m₁ >m₂ and apply Newton’s second law to each object we have m₁g – T = m₁a for the first object and T-m₂g =m₂a for the second object. Solving these equations for a and T gives 𝑎 = (𝑚₁−𝑚₂)/(𝑚₁+𝑚₂)𝑔 and 𝑇 = (2𝑚₁𝑚₂)/(𝑚₁+𝑚₂)𝑔."
 

“In the analysis of the Atwood machine it is assumed that the masses of the pulley and cord are negligible and the friction in the pulley bearings can be neglected. The demonstration model is designed to minimize these spurious effects. In particular the pulley axle rests on the circumference of two large wheels which rotate much more slowly than the pulley. This arrangement reduces bearing friction. It is necessary to level the Atwood machine carefully to prevent the cord from leaving the pulley. This equipment is very old and is probably not worthwhile to attempt a quantitative exercise with the apparatus. It is quite effective, however, as a model showing the motion qualitatively.” - Gordon Danielson, August, 1977

Video Demonstration

There are no spoken words with this recording.