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🟢 8: T 10/20 - pulleys (Atwood machines & modified Atwood)
🟢 8: T 10/20 - pulleys (Atwood machines & modified Atwood)
Today, we'll continue talking about ideal pulleys and how they just change the direction of force. We'll finish out the unit by taking a look at the "Atwood machine" and the "modified Atwood machine" and apply what we know about two-body systems to this very similar pulley problem. We'll do some sample problems together as a class.
Watch the videos posted below and try to continue Situation 3 of the Two Block Systems Activity that we started last time by looking at Atwood machines and modified Atwood machines. In your journals, draw your free body diagrams, write Newton's 2nd Law, and manipulate those equations to get expressions for acceleration and contact force (tension) between the cart and the hanging mass. Get to a point where all you will have to do is to record the actual masses to calculate your predicted variables. UPLOAD A PICTURE OF YOUR WORK TO GOOGLE CLASSROOM. We'll continue taking data next class.
Optional Extra Practice: page 5 of Big Newton's Law Packet. (SOLUTIONS to whole packet)
Homework: Complete your work for getting predicted acceleration and contact force between carts in parts 1 and 2 of the Two Block Systems Activity. You should have already finished and submitted work for part 3 by drawing your free body diagrams, writing Newton's 2nd Law, and manipulating those equations to get expressions for acceleration and contact force (tension) between the cart and the hanging mass. Review your notes from the last few days on Newton's 3rd Law, and bring your questions to class. ❗Assessment of all of Newton's Laws in 1-D on Tuesday, October 27th.
If you missed class or need a refresher, please watch this video on the Atwood machine. Remember that the tensions on both strings are the same only if you have an "ideal pulley," which is a massless pulley on a frictionless axle.
Make sure you watch the whole video to see that it's possible to draw a free body diagram of "the system" including both masses and the string. How would you pick a sign convention that adequately conveys the motion? Remember that in a force diagram, you only draw EXTERNAL forces to that system (internal forces are not shown). In these kinds of problems, usually you only need to use 2 of the 3 FBDs in order to completely solve the problem.
Then, watch this video on the modified Atwood machine. Remember that the tensions on both vertical and horizontal strings are the same only if you have an "ideal pulley," which is a massless pulley on a frictionless axel.
🟩 8: W 10/21 - two block activity (part 2)
🟩 8: W 10/21 - two block activity (part 2)
Today, you'll have the opportunity to finish the Two Block Systems Activity:
Complete Situations 1 & 2:
Record data on the experimental accelerations and contact forces between the carts.
Compare the above to your predicted values.
Complete Situation 3:
You should have already draw your free body diagrams, written Newton's 2nd Law, and manipulated those equations to get expressions for acceleration and contact force (tension) between the cart and the hanging mass.
Record data on masses.
Caluculate the predicted values for predicted acceleration and predicted contact force (tension).
Take data on the experimental accelerations and contact forces between the carts.
Compare the above to your predicted values.
Then after you have completed the activity, we'll work on problem solving from the test bank. Specifically, we'll look at Newton's 3rd Law problems and multi-mass systems including pulley problems. You may bring your classroom journals home today.
Homework: Continue to work through problems from the test bank. ❗Assessment of all of Newton's Laws in 1-D on Tuesday, October 27th.
💚 8: Th 10/22 - problem solving
💚 8: Th 10/22 - problem solving
Today, we'll work on problem solving from the test bank. You may bring your classroom journals home today. Catch up on any test bank problems you still have not completed.
Homework: Continue to work through problems from the test bank. ❗Assessment of all of Newton's Laws in 1-D on Tuesday, October 27th.
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