**PIRA 1G10.40 Force, Mass, and Acceleration: Atwood's Machine**

**Instructions / Notes:**

- A low-friction light pulley and a combination masses (2M + 1m or 2m).

- The apparatus comes with a meter stick and a stop watch.

- Faculty may want to preview the actual demo before ordering.

- The demonstration has two LARGE Masses of (M>)- 200 grams each.

- Two or four little masses - 5 grams each - which can be transferred.
- Each little mass is symbolized as (m) in the examples below.

- Example: 1(M) versus 1(M) plus 2(m) on opposing side.
- Total mass of both sides together = 410 grams

- Example 2 below is for someone who wants to use class time to make 2 measurements.
- To do 2 measurements, four little masses of 5 grams each are needed.

- Example 2: 1(M) plus 1(m) on one side versus 1(M) plus 3 (m) on the opposing side.
- Total mass of both sides together = 420 grams

- Example 2, part B: 1(M) on one side, then 1M plus four 5 gram weights on the other.
- Total mass of both sides together on this second run = 420 grams

- Once again, LARGE (M) = 200 grams and each little (m) = 5 grams

- The image shows each 200 gram mass containing the same number of 5 gram masses.

- The demo number in the image should be labelled 1G10.40 not 5G10.40.

- A stopwatch is used to measure the time it takes (B) to fall 1 meter.

**Demo Staff:**Start with (M + 2m) on each side.

*Last Updated 3/10 - University of Texas at Austin Physics
Dept. - All Rights Reserved.*