badmintondr

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Dec 10, 2009
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I know this is also probably another ******ed post by me but can someone clarify as to whether or not TBR covers this in enough depth. I personally feel like it's lacking in terms of content seeing as how it is so short. Furthermore, I'm irked, pissed, frustrated, and probably not thinking clearly. But, I've tackled this chapter on 3 different occasions and always end up in this frustrated attitude. I know I'm stupid already but this chapter is making me feel downright ******ed. I'm doing the passages and getting completely crushed. It's also not helping considering that the concepts seem simple enough but when it comes down to application of the concepts, I seem to be completely wrong.

Take Passage 4 for example, I pretty much got everything wrong conceptually. I don't understand how changing the coiling direction will result in a different upwards or downwards torque or which direction is associated with which coiling?
How does the weight go up and down relative to spinning?

For 25, answer choice B, I don't understand how it is not true. Also, I don't understand how the answer states that adding an external force would tip it easier because it has a higher center of mass but why would i even consider adding an external force in the first place.

Also, has moment of inertia been covered in chapters 1-3 because I didn't see it or I didn't know who to apply it for this question. I know intertia is an object's innate ability to resist change but I don't understand moment of inertia.

Thanks.
 
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BerkReviewTeach

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I know this is also probably another ******ed post by me but can someone clarify as to whether or not TBR covers this in enough depth. I personally feel like it's lacking in terms of content seeing as how it is so short. Furthermore, I'm irked, pissed, frustrated, and probably not thinking clearly. But, I've tackled this chapter on 3 different occasions and always end up in this frustrated attitude. I know I'm stupid already but this chapter is making me feel downright ******ed. I'm doing the passages and getting completely crushed. It's also not helping considering that the concepts seem simple enough but when it comes down to application of the concepts, I seem to be completely wrong.

Take Passage 4 for example, I pretty much got everything wrong conceptually. I don't understand how changing the coiling direction will result in a different upwards or downwards torque or which direction is associated with which coiling?
How does the weight go up and down relative to spinning?

For 25, answer choice B, I don't understand how it is not true. Also, I don't understand how the answer states that adding an external force would tip it easier because it has a higher center of mass but why would i even consider adding an external force in the first place.

Also, has moment of inertia been covered in chapters 1-3 because I didn't see it or I didn't know who to apply it for this question. I know intertia is an object's innate ability to resist change but I don't understand moment of inertia.

Thanks.
Passage 4 is a doozie, and a perfect example of how AAMC writers can mess with you by presenting a bizzare device that looks unfamiliar at first. What could help is thinking about a yoyo. As you drop it, it accelerates, spinning faster and faster as the string uncoils until it reaches its lowest point. From here, the yoyo is still spinning, so the string winds around the axis once again, causing the yoyo to climb up the string. Once at its highest point, it stops spinning. It should go back down, uncoiling in the opposite direction of what it just did.

The passage shows falling weight that is connected to a sideways yoyo. As the weight falls, the spindle turns and like a yoyo is spinning fastest when the weight reaches it lowest point. Because the spindle is turning fast at this point, it reels the string in (like a yoyo) and pulls the weight back up.

The movable masses connected to the spindle are there just to make the system screwier by providing resistance to spinning. Hopefully this helps to visualize what is going on. It's a damn tricky passage, but a few of the concepts are clearer with this visualization.