Atwood Machine Force Problems (Pulleys)

How to Solve Atwood Machine Force Problems (Pulleys)s

This video gives you an overview of how to work Atwood Machine problems, which are basically any force problem where you have masses and pulleys. Just like with multiple objects getting pushed or pulled, you'll need to do a free body diagram of each mass. You may even need to do a free body diagram of the pulley. And check out how the coordinate systems go opposite directions for the two masses!

Atwood Example - Two Masses Hanging Vertically From Pulley

This video covers the most basic Atwood Machine example which every class uses (and which I still remember showing up on my first college physics exam as well!). Whether the two objects are anonymous masses, or a monkey and a crate of bananas (my exam again), the process is the same as this general example. I highly recommend watching this one before anything else below.

Atwood Machines - Hanging Mass Pulling Object Across Level Surface

This example is the second most common Atwood Machine problem: a hanging mass dragging a second mass across a level, frictionless table.

Atwood Example - Hanging Mass Pulling Weight Up Inclined Plane

To take our Atwood Machine excellence one notch further, how about throwing an "inclined plane" (a.k.a. ramp problem) into the mix!

Atwood Machine with Three Masses

Adding a third mass to an Atwood Machine problem doesn't increase the difficulty of the physics much, but it does make sure you know how to do these problem correctly because it's even more critical to put your coordinate systems in correctly. And having to solve a system of three equations and three unknowns isn't exactly a recipe for *not* making algebraic mistakes.

Atwood Machine - Two Masses On Two Inclined Planes

So many classic Atwood Machine problems, so little time! In this one, two inclined ramps are set up back-to-back with a massless rope and pulley connecting them, then they do a tug-o-war! Who will win! Who will lose! One is heavier but one has a steeper angle! The suspense is killing me!

Calculating Tension & Advantage of Pulley Systems

This video explains how to tell the difference between pulley systems. Of the three systems in the video to the right, one system requires the person to pull up the full weight of the mass, one requires a pull of just half the weight, and one requires you to pull with DOUBLE the weight. Which is which? And how far would you have to pull the rope in each?

How to Tell The Difference Between A Pulley System vs Just A Bunch of Pointless Pulleys

This video tries to give you the tricks for spotting when a pulley system is giving a "pulley advantage" (meaning with a given force of tension you can lift a much heavier mass), as opposed to just making the rope snake through a bunch of fixed pulleys without making the job at hand any easier.

This problem may not *look* so much worse than the others above it on this page, but believe me, it's nuts. Not only do you have to do a separate free body diagram on the pulley, you have to make some pretty magical assumptions about the accelerations of the two masses.

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