Physlet Illustration: Atwood's Machine

m1 = kg
m2 = kg

 

 

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Two boxes of unequal mass are connected by a light string that passes over a massless, frictionless pulley, as shown. The boxes start from rest, and the velocity of the box on the left is given in m/s. Adjust the masses (1 kg < m1,m2 < 10 kg) and measure the acceleration of the system. Can you determine the tension in the string?

Hints

  1. How do the accelerations of the two boxes compare?
  2. Can you draw a free-body diagram for each box?
  3. What force results in a box's acceleration?
  4. Apply Newton's 2nd Law to each box's motion, equating that force to the product of mass times acceleration.

Reference

See Walker, Section 6-4

Illustration written by Steve Mellema