Atwood's Machine

Two equal masses are connected with a string over a pulley. If an additional small mass is added to one side, the system will accelerate in that direction. This can also be setup with two pulleys. Acceleration, Force, and Tension can be discussed when examining this system.

Setup:

Suspend the pulley above the lab table using the ring stand and clamps. Tie a piece of string between the two mass hangers. (Be sure it is an appropriate length so that one mass hanger can be on the table and the other still hangs below the pulley.)

Place equal mass on the mass hangers. The system will remain the same unless perturbed.

Place an additional small mass on one side and that mass will accelerate downward.

Include a spring scale for measuring force.

Notes:

None

Courses Used In:

• PHY 10111

• PHY 10310

• PHY 10410

• PHY 20454

• PHY 30210

Discussion and Physics Polling/Clicker Questions:

• Is the acceleration of the rising mass the same as of the falling mass?

• Is the force the same on the rising mass as on the falling mass?

• If a connected mass is falling, is it in free fall (i.e. a = g)?

• Is the tension in the string where it connects to mass 1 equal to where it connects to mass 2?

• Does the acceleration depend on the initial positions of the masses (if one is higher than the other)?

Equipment Needed:

• Ring Stand with Clamp

• Pulley

• String

• Spring Scale

• Two Mass Hangers

• Two Equal Masses (200 g)

• One Small Mass (20 g)