FizziksGuy

How do high jumpers use center of mass to maximize the height they can clear?

Sounds like a good start... might be worth reviewing what motion is just to be clear moving forward. We'll keep practicing so these make more and more sense!

Exactly... T1 as in the tension due to mass 1, and T2 is the tension due to mass 2. Also, don't forget that you need to use 9.8 for g in the WebAssign problems.

Keep in mind that you have two torques still on the wheel, so: . Combine that with Newton's 2nd Law equations for both mass 1 and mass 2 and you'll have a system of equations you can solve to obtain your answer. :banghead)

APlusPhysics Blogs and Forums have now been integrated with Facebook! Not only can you link your accounts, but you can simultaneously post any forum messages, blog entries, and comments to your Facebook wall by checking the "Publish to Facebook" checkbox at the bottom of your entry. Further, you also have the ability to "Like" blogs and forum posts... I'm interested to see if this encourages discourse and engagement by integrating a student favorite social networking site with classroom content.

Wish I could re-design the tongue channel on a couple dogs I know...

APlusPhysics forums and blogs have now been integrated through Facebook Connect! This means you can share your blog posts and comments, forum posts and comments, and "Like" button information on your facebook account. Check it out by clicking on the "Facebook Connect" button on the top of the page. If you want to share your posts on facebook, make sure to check the "Publish to Facebook" checkbox before hitting submit.

That's quite a unique perspective... I wonder what other everyday phenomena we could look at in a whole new light by changing our frame of reference?

Software (cookie) settings have been updated to allow you an hour and 20 minutes before you're automatically logged off in the future. Hopefully this will prevent you having the same frustration again.

Sounds like a good start... how are you feeling after a couple more days of letting it sink in? Remember period (T) is the time for one complete revolution (take total time, divide by number of revs) and frequency is the number of revs per second (take # revs, divide by total time). If you know one, you can find the other: You can also check out the review guide (with examples) on Frequency and Period here: http://www.aplusphysics.com/courses/regents/circmotion/ucm.html#freqper

You just needed a space after the [tex] tag... least I could do was clean that up after your argument with the login timeout earlier tonight!

Recently Frank Noschese, a NY physics teacher (Cornell) with a strong background in modeling and standards-based grading and author of the popular blog "Action-Reaction," was nominated for "Most Influential Blog Post" in the 2010 Edublog awards. The post, "The $2 Interactive Whiteboard," is a great resource for teachers looking to get into modeling and white boarding cheaply and easily. Help him win the award and, more importantly, spread the message about modeling in physics education by voting at: http://edublogawards.com/2010awards/most-influential-blog-post-2010/ :einstein)

What factors do you think ought to be considered?

Glad to hear you're able to catch up on the material. Prof. Lewin does an amazing job, and if you watch his lectures, you see almost the exact thing we do in class (at least in this unit)... he's as good, if not better, than anyone I've seen in lecturing about rotational motion and angular momentum.

I'm betting he followed the direction in this post from our forums: http://www.aplusphysics.com/forums/showthread.php?15-Embedding-formulas-into-your-posts.

Great post willorn! By the way, if you're interested in superconducting magnetic levitation, it just so happens that I've managed to pick up a disc of Yttrium Barium Copper Oxide... we could videotape a demonstration and explanation for the Physics In Action podcast -- just need to pick up some liquid N2, which isn't tough to do with a bit of advance planning!

Awesome analysis and a creative way of applying what we're learning to a VERY big scenario. Well done! :wave)

You're not alone in your thoughts. Our unit on rotation and angular momentum will be, by far, the most difficult of the entire mechanics course. Not only is the material new, it utilizes calculus you're just learning, and it is by no means intuitive -- in many cases, it's just the opposite, actually (angular momentum is just one of those things that doesn't really fall into our everyday conceptualization easily). Very shortly, as we get into the heavier stuff, we'll slow down the amount of material being thrown at you each day and balance it with lots and lots of practice so you start to feel more comfortable with it.

Great find Alex -- these are the videos I highlighted in your independent work unit. Our version of AP-C physics is, in many ways, based on Dr. Lewin's lectures. In creating the course format, I relied heavily on his lecture series myself. Good stuff, and a highly entertaining professor. His unit on rotational kinematics and angular momentum are by far the best I've seen, so you'll see our work in class highly correlated with his videos over the next couple weeks! By the way, for those of you with iPods and iPhones, these online lectures are available for free download to watch on your iPod through iTunes...

I've never considered the physics of a dragon before... They'd make great study subjects for kinematics... or even thermodynamics!!!

I had the opportunity to meet with a colleague, teacher, friend and peer on Wednesday, and I'm thrilled with how our breakfast (and work meeting) progressed. Having known each other professionally for close to 10 years now, from a time back before either of us entered education, it was a tremendous experience to sit down and talk about what's working in our classrooms, what we envision for the future, and start putting plans together to achieve that vision. Following breakfast, we settled down to work by looking over what had been completed so far at APlusPhysics.com. I was amazed at how closely our visions aligned... although I probably shouldn't have been since this colleague, in many ways, provided some of the grounding for this website project in the first place. We then spent the better part of four hours working on various parts of the website, each of us contributing in our own ways. I look forward to seeing what we can build together, and am very excited to have another viewpoint for input, contribution, and criticism as we move forward. Thanks Tom!

Had a busy weekend with lots of small successes on the APlusPhysics front... First off, finished up the first draft of the Regents --> Graphing Motion page (http://www.aplusphysics.com/courses/regents/kinematics/reg_graphmotion.html) with a couple more sample problems and an interactive Flash mini program demonstrating the relationship between d-t, v-t, and a-t graphs (thanks to Tom Schulte for the great graphics!!!). Also, spent some time on the phone with a physics teacher in Illinois working on an article that details our forensics and physics day activity -- received some terrific input and ideas that will definitely improve the article. Plus, it's always nice to make another friend in the physics teaching field. Then, got a start on the Regents --> Kinematic Equations page... lots of blanks to fill in and still tons of editing and re-organizing to do, but I'm feeling good about getting first drafts created and posted. Hopefully I can keep this momentum going with some time off during the holiday week. Finally, I'm pleased to see the "Homework Help" section of the website getting some use... not only are those asking questions getting the help they need without having to wait for class time, but those who are providing the help are reinforcing physics concepts. "The best way to learn is to teach!"

Great response... Moe is absolutely right. Remember, no net force doesn't mean an object is at rest. no net force means an object won't accelerate -- therefore an object at rest will remain at rest, and an object in motion will remain in motion at a constant velocity and in a straight line -- unless there is a net force. For example, if a spaceship is moving at 1000 m/s through space, if Superman pushes it forward with a force of 50N and The Hulk pushes it backward with a force of 50N, the forces are balanced, so there is no net force, therefore the spaceship continues at 1000 m/s. Net force = 0 implies no acceleration.

You might have to play for a bit to determine the angles (the math gets a bit more involved), but it's pretty straightforward to see how you could line up a 4N, 4N, and a 5N vector to achieve equilibrium... I've used the vector simulation lab from PHET (http://phet.colorado.edu) to demonstrate how putting a 4N, 4N, and 5N vector together gives you a vector sum of 0. [ATTACH=CONFIG]52[/ATTACH]