course phy 201
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14:50:45 How do flow diagrams help us see the structure of our reasoning processes?
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RESPONSE --> Flow diagrams help us to see the structure of our reasonsing processes by showing how all of these equations are interwoven together in a clearly legible form
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14:50:56 ** They help us to visualize how all the variables are related. Flow diagrams can also help us to obtain formulas relating the basic kinematic quantities in terms of which we have been analyzing uniformly accelerated motion. **
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RESPONSE --> Correct
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14:57:38 How do the two most fundamental equations of uniformly accelerated motion embody the definitions of average velocity and of acceleration?
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RESPONSE --> The two fundamental equations, v= a * h and vAve = 'ds /'dt embody the definitoins of average velocity and acceleration becayse they show the position of change is equal to the change and time required
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14:57:50 ** Velocity tells us the rate at which the position changes whereas the acceleration tells us the rate at which the velocity is changing. If acceleration is uniform ave velocity is the average of initial and final velocities. The change in position is found by taking the average velocity vAve = (vf+ v0) / 2 and multiplying by the'dt to get the first fundamental equation `ds = (v0 + vf)/2 * `dt. The acceleration is accel = rate of change of velocity = change in velocity / `dt = (vf - v0) / `dt. In symbols this equation is a = (vf + v0) / `dt. Algebraic rearrangement gives us this equation in the form vf = v0 + a `dt. This form also has an obvious interpretation: a `dt is the change in velocity, which when added to the initial velocity gives us the final velocity. **
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RESPONSE --> correct
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15:00:20 How can we interpret the third fundamental equation of uniformly accelerated motion?
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RESPONSE --> We interpret the third fundemental equation of uniformyl accelerated motion by 'ds = vAve * 'dt tahat displacement can be obtained form average velocity and time interval.
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15:00:26 ** The third equation says that `ds = v0 `dt + .5 a `dt^2. This means that the displacement `ds arises independently from initial velocity v0 and acceleration a: v0 `dt is the displacement of an object with uniform velocity moving at velocity v0, and 1/2 a `dt^2 the distance moved from rest by a uniformly accelerating object. The two contributions are added to get the total `ds. **
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RESPONSE --> Ok
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15:04:54 Why can we not directly reason out the basic 'impossible situation'?
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RESPONSE --> We cannot directly reason out the basic 'impossible situation' where only v0 is known, a and 'ds. There is no way to directly reason out vAve or 'dv or any other variables needed.
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15:05:03 ** In this situation we know v0, a and `ds. From v0 and a we cannot draw any conclusions, and the same is true for v0 and `ds and also for a and `ds. No pair of variables allows us to draw any additional information. **
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RESPONSE --> Correct
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15:13:06 What strategy will we use to reconcile the basic 'impossible situation'? WE cann write down the 2 most fundamental equations and see what we do know.
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RESPONSE --> Knowing the two fundamental equations are 'ds = (vf0 + v0) /2 * 'dt and a = (vf- v0) /'dt. It is already known that given 'ds, dt, or v0, and vf will give us the values of any variables. However somtimes linear equations must be used like vf^2 = v0^2 + 5 'ds and 'ds = v0 'dt + .5 a 'dt^2
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15:13:14 ** We can use the fourth equation vf^2 = v0^2 + 2 a `ds to obtain vf, then knowing the values of v0, vf, a and `ds we easily find `dt either by direct reasoning or by using one of the fundamental equations. **
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RESPONSE --> correct
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15:16:34 What is the difference between understanding uniformly accelerated motion and analyzing it with the use of equations?
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RESPONSE --> The difference between understanding uniformly accelerated motion and analyzing it with use of equations is that understand the basic use of acceleeration in our daily lives leads us to undersand why the equations are importnt and how we can manipulate them to solve problems
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15:16:43 ** You can use equations without understanding much of anything. To use the equations you don't even need to understand things like average velocity or change in velocity. You just have to be able to identify the right numbers and plug them in, which is an important task in itself but which doesn't involve understanding of the physical concepts behind the equations. **
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RESPONSE --> Ok
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15:19:48 How do we extrapolate our acceleration vs. ramp slope data to obtain an estimate of the acceleration of gravity?
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RESPONSE --> we extrapolate our acceleration vs. ramp slope data to obtain an estimate of the acceleration of gravity by finding the coordiantes between position and clock time
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15:19:54 ** We can sketch a straight line as close as possible to our data points. Then we use the average slope of that graph; this average slope is the acceleration of gravity. **
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RESPONSE --> Ok
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15:23:24 How do the unavoidable timing errors due to the uncertainty in the computer timer affect our estimate of the acceleration of gravity?
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RESPONSE --> I do not understand this question
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15:25:38 ** STUDENT ANSWER: This error causes the slope to increase at an increasing rate rather than form a linear line. INSTRUCTOR COMMENT: Good answer. A systematic error would do that. Even random, non-systematic errors affect the placement of points on the graph, and this tends to affect the slope of the straight line approximating the graph, and also to reduce the accuracy of this slope. **
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RESPONSE --> Ok
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15:26:16 ** STUDENT ANSWER: This error causes the slope to increase at an increasing rate rather than form a linear line. INSTRUCTOR COMMENT: Good answer. A systematic error would do that. Even random, non-systematic errors affect the placement of points on the graph, and this tends to affect the slope of the straight line approximating the graph, and also to reduce the accuracy of this slope. **
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RESPONSE -->
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15:27:55 How could the slight slope of the table on which the ramp rests, if not accounted for, affect our graph of acceleration vs. ramp slope but not our estimate of the acceleration of gravity?
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RESPONSE --> The slight slope could affect the acceleration of the object moving, but gravity is constant
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15:28:21 ** GOOD STUDENT ANSWER: The only effect this systematic error has on the graph is to change the m coordinate of each point by an amount equal to the slope of the table, which is always the same.Since it is the graph slope that comprises our final result, a small table slope would have no effect on our conclusions. **
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RESPONSE --> Ok
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15:31:54 How could anticipation of the instant at which a cart reaches the end of the ramp, but not of the instant at which it is released, affect our graph as well as our estimate of the acceleration of gravity?
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RESPONSE --> we can caluculate accelertation by subtracting the final velocity by the initial velocity and dividing byt the change in clock time.
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15:32:03 ** GOOD STUDENT ANSWER: The timer is started with a slight delay due to the reaction time of the person doing the timing. This would be OK if the individual's reaction time caused the individual to stop the timer with the same delay. However, the person doing the timing often anticipates the instant when the cart reaches the end of the ramp, so that the delay is not added onto the end time as it was to the starting time. The anticipating individual often triggers the timer slightly before the cart reaches the end, compounding the error even further and also causing the graph to curve rather than remain linear. **
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RESPONSE --> Ok
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Ꙭַ[£QxsΡ assignment #007 呌騶~Q Physics I Class Notes 06-09-2006
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15:48:24 Why do we say that the first equation of uniformly accelerated motion expresses the definition of average velocity, while the second expresses the definition of acceleration?
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RESPONSE --> The first equation expresses average velocty with 'ds = (vf + v0) /2 * 'dt and characterizes a uniform acceleration with these specific paramerters. Othe rpaarameters distinguish the definition of acceleration through a = (vf-v0)/'dt
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15:48:31 ** When acceleration is uniform average velocity is the average of initial and final velocities, (vf + v0) / 2. Average velocity is `ds / `dt (whether accel is uniform or not). Setting `ds / `dt = (vf + v0) / 2 we obtain `ds = (vf + v0) / 2 * `dt, which is the first equation of uniformly accelerated motion. So the definition of average velocity is equivalent to the definition of average velocity. Average acceleration is aAve = `dv / `dt = (vf - v0) / `dt. Since for uniform acceleration the acceleration is constant, we can just say that in this case a = (vf - v0) / `dt. This equation is easily rearranged to give the second equation of motion, vf = v0 + a `dt. **
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RESPONSE --> Ok
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16:22:58 Why, for uniform acceleration, is vAve = (vf + v0) / 2, while this is not usually true for nonuniform acceleration?
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RESPONSE --> vAve = (vf + v0) / 2 is true for uniform motion but not nonuniform motion because changes in acceleration lead to caluclating the changes in velocity, not he average
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16:23:07 ** If acceleration is uniform then the v vs. t graph is linear, so that the average velocity over any time interval must be equal to the velocity at the midpoint of that interval. It follows that the average velocity must be midway between the initial and final velocities. (vf + v0) / 2 is the average of the initial and final velocities, and is therefore halfway between the v0 and vf. **
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RESPONSE --> Ok
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16:23:55 In commonsense terms, why does change of velocity over a given distance, with a given uniform acceleration, differ with initial velocity?
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RESPONSE --> The initial velocity does not change one the initial value is taken, where as change of velocity may flucation with acceleration
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16:24:00 ** If the uniform acceleration is the same in both cases, then assuming that both initial velocity and acceleration are positive, a greater initial velocity will result in a shorter time interval to cover the given distance. A shorter time interval leaves less time for velocity to change, resulting in a smaller change in velocity. **
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RESPONSE --> Ok
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