A half-Atwood’s machine (also called a modified Atwood’s machine), with a cart, string, pulley, and hanging mass, is a common Newton’s Second Law and kinematics lab. The following video demonstrates how to attach the Pulley Bracket (B-SPA) and Ultra Pulley Attachment (SPA) to the track.

Some details to note:

  • The Pulley Bracket comes with two thumb screws. If you are attaching the Ultra Pulley, use the shorter thumb screw. (When attaching both a photogate and the Ultra Pulley use the longer thumb screw; see How do I attach a Photogate and Ultra Pulley to the end of a Vernier Track?)
  • The Pulley Bracket slot allows you to adjust the height of the Ultra Pulley above the top surface of the track. If you are using the pulley in a half-Atwood setup, lower the Ultra Pulley to a position where the string – connected to the cart on one end and a hanging mass on the other – is parallel to the track; in that position, the force exerted by the string is horizontal, i.e. does not have a vertical component.

Cart and Track System Troubleshooting and FAQs
Vernier Photogate (VPG-BTD) Troubleshooting and FAQs