course Phy 201 I was a little confused when it came to the query. Assignment 8 had questions from chapter 2, 3, and 4. The only questions from chapter 4 appeared in the Query. That was very confusing to me because I thought the query is supposed to quiz you of the information from the assignment. From the previous assignments we are just answering the questions in the book for Chapter 2. Are we using the same book? I have edition 6 that I purchased at the book store. I just want to make sure that we are on the same page because I am beginning to get a little confused. Thanks! Òxž’±•Àš¢Úã|Ñ»é¿ Š’ʆassignment #008
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17:02:56 QUESTION FROM STUDENT--Please define the differnece between Fnet and Force. See if you can answer this question.
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RESPONSE --> Force is defined as any push or pull on an object. Fnet is the total amount of forces acting upon an object or the sum of all forces. confidence assessment: 3
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17:03:44 ** Net force is the sum of all forces acting on an object. If you're pushing your car you are exerting a force, friction is opposing you, and the let force is the sum of the two (noting that one is positive, the other negative so you end up with net force less than the force you are exerting). Your heart rate responds to the force you are exerting and the speed with which the car is moving; the accel of the car depends on the net force. **
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RESPONSE --> ok self critique assessment: 3
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17:09:48 In terms of the equations of motion why do we expect that a * `ds is proportional to the change in v^2, and why do we then expect that the change in v^2 is proportional to Fnet `ds?
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RESPONSE --> The acceleration of an object is directly proportional to the net force acting on it, and is inverasely proportional to its mass. The direction of the acceleration is in the direction of the net force acting on the object. This is Newton's second law of motion. confidence assessment: 2
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17:11:25 ** It's very important in physics to be able to think in terms of proportionality. To say that y is proportional to x is to say that for some k, y = k x. That is, y is a constant multiple of x. To say that a * `ds is proportional to the change in v^2 is to say that for some k, a * `ds = k * ( change in v^2)--i.e., that a * `ds is a constant multiple of the change in v^2. In terms of the equations of motion, we know that vf^2 = v0^2 + 2 a `ds so a `ds = 1/2 (vf^2 - v0^2), which is 1/2 the change in v^2. So a `ds is a constant multiple (1/2) of the change in v^2. Formally we have a `ds = k ( change in v^2) for k = 1/2. Now since Fnet = m a we see that Fnet is proportional to a for a given mass m, and it follows that Fnet `ds = k * change in v^2, for the appropriate k (specifically for k = mass / 2. **
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RESPONSE --> ok self critique assessment: 3
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17:12:47 How do our experimental results confirm or refute this hypothesis?
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RESPONSE --> I'm not sure what results you are referring to but I would assume that most results would confirm this hypothesis because Fnet is equal to mass times acceleration. confidence assessment: 2
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17:13:09 ** We didn't actually do this part of the experiment, but on a ramp with fixed slope a `ds is simply proportional to `ds. When we measured `dt for different distances from rest down the same ramp, we were then able to determine the average and final velocities. The change in v^2 for each timing would be from 0 to vf^2. The change would therefore be just vf^2. If a `ds is proportional to the change in vf^2 then a graph of vf^2 vs. a `ds should be linear. Since a is constant we don't even need to determine it--a graph of vf^2 vs. `ds would be linear. This would confirm the hypothesis. **
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RESPONSE --> ok self critique assessment: 3
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