Atwood machine

Definition

An Atwood machine is a device consisting of two masses connected by a string that passes over a pulley. It is used to study the principles of dynamics and acceleration in classical mechanics.

5 Must Know Facts For Your Next Test

1. The net force on the system can be calculated as the difference in weights of the two masses, $ (m_2 - m_1) g $, where $ m_2 $ is greater than $ m_1 $.
2. The acceleration of both masses is the same and can be found using $ a = \frac{(m_2 - m_1) g}{m_1 + m_2} $.
3. Tension in the string can be computed using either mass: $ T = m_1(g + a) $ or $ T = m_2(g - a) $.
4. Ideal conditions assume the pulley is frictionless and massless, and the string is inextensible.
5. Atwood machines are used to demonstrate Newton's second law, which states that force equals mass times acceleration ($ F = ma $).

Review Questions

• How do you derive the acceleration formula for an Atwood machine?
• What assumptions are made about the pulley and string in an ideal Atwood machine?
• How do you calculate the tension in the string using one of the masses?

Related terms

Newton's Second Law: States that the force acting on an object is equal to its mass times its acceleration ($ F = ma $).

Tension: The pulling force transmitted along a string, rope, cable, or similar object.

Pulley: A simple machine consisting of a wheel over which a rope or chain is pulled in order to lift heavy objects.