Atwood Lab Homework: Analyze, Experiment & Report

[o0griff0o]

Homework Statement

So I have this lab and I have no idea how to come about doing this.

An Atwood machine consisting of two massless pulleys (one smart pulley without friction and one pulley with friction) and hanging masses will be provided, as shown in the diagram below. you will be given specific quantities to solve for experimentally, using the Atwood machine.
Analyze the Atwood machine system shown and understand all of the physics involved. I will have only a few minutes in class to discuss the experimental problem and the technique to be used with your group, a few minutes to collect appropriate data with your group, and enough time to analyze your data individually and submit a short report. Good experimental technique will receive more points.

http://i601.photobucket.com/albums/tt92/…

Homework Equations

F= ma T= I(alpha) Inertia for a disk = 1/2 MR^2

The Attempt at a Solution

Umm I was thinking either to split this up into a net torque or a F=ma type of thing, but I was wondering how can a Pulley that is mass less have friction? Also Any ideas in gernal on how to go about with this lab?

 

[o0griff0o]

ok so I set up torque equations at different points starting from right to left of the diagram.
starting at mass M1
1) T4-m1g=m1a
At the pulley connected to M1
2)-T4(r) + T3 (r) = (1/2 Mr^2)(a/r)
At the second pulley
3) -T2(r)+T1(r) = (1/2 Mr^2)(a/r)
then at m2
T1-m2g = m2a

Now The question says that there is friction so how would i incorparate that into equation 2?

Also I saw that the picture link was no working so here is another link to it http://i601.photobucket.com/albums/tt92/o0griff0o/atwoodmachine.png

 

[o0griff0o]

Can I also assume that the acceleration throughout the whole system is equal?

 

[gneill]

Can I also assume that the acceleration throughout the whole system is equal?

Presumably the string is "light and inextensible", so that the linear acceleration should be everywhere the same assuming that the string remains taught.

Regarding the friction, it will behave as a torque on the pulley so you can model it as such. You should be able to fill in the details for it once you have them.

Also, if the pulleys really are massless as stated, then you might want to consider the implications for your equations involving their moments of inertia!

 

[rwisz]

I understand your confusion and am here to help guide you through this lab. First, let's start by looking at the equipment provided and understanding the physics involved. The Atwood machine is a simple mechanical device that allows us to study the effects of gravity and mass on an object. In this case, we have two masses hanging from a pulley system.

Now, let's address your question about the pulley with friction. While the pulley itself may be massless, there could be some amount of friction present at the axle or bearings of the pulley. This friction can affect the motion of the system and should be taken into consideration during your analysis.

To approach this lab, I would suggest starting with a free body diagram for each of the masses and using Newton's second law (F=ma) to analyze the forces acting on each mass. You can also consider the torque on the pulley using the equation T=I(alpha), where I is the moment of inertia and alpha is the angular acceleration.

During the lab, make sure to use good experimental technique, such as taking multiple measurements and averaging them to reduce error. And don't forget to include units in your calculations and final report.

I hope this helps and good luck with your lab! Remember, as a scientist, it's important to approach problems with curiosity and a willingness to explore and experiment.