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Your 'initial timing experiment' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
** Initial Timing Experiment_labelMessages **
I apologize for these submissions taking so long but the weather last week affected my internet and it's taken a while to fix. I should be able to submit all of my work including this weeks by the end of the week.
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Note: The majority of student report taking less than an hour on this experiment, though a few report significantly longer times.
Take reasonable care to get good data in this experiment. Try to do the timing as accurately as possible. Measurements of length, height, etc. should be reasonably accurate (e.g., with a meter stick or ruler you can measure to withing +- 1 millimeter, but it's not necessary to try to determine fractions of a millimeter).
In this experiment you will use the TIMER program, a hardcover book, the toy car that came in your lab materials package (or, if you do not yet have the package, a cylinder or some other object that will roll along the book in a relatively straight line), and a ruler or the equivalent (if you don't have one, note the Rulers link, which is also given on the Assignments page).
The book's cover should be straight and unbent.
The toy car (or other object) should roll fairly smoothly.
Place the book on a flat level tabletop. You will prop one end of the book up a little bit, so that when it is released the object will roll without your assistance, gradually speeding up, from the propped-up end to the lower end. However don't prop the end up too much. It should take at least two seconds for the ball to roll down the length of the book when it is released from rest. For a typical book, a stack of two or three quarters placed under one end works well.
Using the TIMER program determine how long it takes the ball to roll from one end of the ramp to the other, when released from rest. Once you've got the book set up, it takes only a few seconds to do a timing, so it won't take you long to time the object's motion at least three times.
Determine how far the object travels as it rolls from its initial position (where you first click the timer) to its final position (where you click at the end of the interval). This will probably be a bit less than the length of the book, due to the length of the object itself.
Determine how much higher one end of the book was than the other, and how far it is from the supports (e.g., the stack of quarters, or whatever you used to support one end) to the end of the book which rests on the table.
Then reverse the direction of the book on the tabletop, rotating the book an its supports (e.g., the stack of quarters) 180 degrees so that the ball will roll in exactly the opposite direction. Repeat your measurements.
In the box below describe your setup, being as specific as possible about the book used (title, ISBN) and the object being used (e.g., a can of vegetables (full or empty; should be specified) or a jar (again full or empty); anything round and smooth that will upon release roll fairly slowly down the incline), and what you used to prop the object up (be as specific as possible). Also describe how well the object rolled--did it roll smoothly, did it speed up and slow down, did it roll in a straight line or did its direction change somewhat?
your brief discussion/description/explanation:
For the book I used About Philosophy, 10th edition, ISBN13:978-0-205-64518-3.
For my rolling object I used the supplied Hot Wheels car which rolled smoothly and in a straight line.
For my book prop I used a stack of 5 pennies
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In the space indicated below report your data. State exactly what was measured, how it was measured, how accurately you believe it was measured and of course what the measurements were. Try to organize your report so the reader can easily scan your data and identify any patterns or trends.
your brief discussion/description/explanation:
Book Elevation:.008 m measured by ruler
Book Length: .24 m measured by ruler
Book Width:.02 m measured by ruler
Car Mass: 56.7 grams gathered from online sources
Travel Time: 2.1 seconds measured using timer
Force: 9.8m/s
a=f/m= 9.8/56.7=.17m/s^2
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It's good that you are familiar with Newton's Second Law.
However force is not measured in m/s, and dividing m/s by grams does not result in an acceleration in m/s^2.
It appears to me that the ball traveled .24 m in 2.1 seconds.
Up to the line where you indicate force you have good data. The last two lines, however, don't correspond to the situation you measured.
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Using your data determine how fast the object was moving, on the average, as it rolled down the incline. Estimate how accurately you believe you were able to determine the object's average speed, and give the best reasons you can for your estimate of the accuracy.
your brief discussion/description/explanation:
Average speed was determined by dividing the overall distance/overall time.
.24 m/2.1 s= .11 m/s
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How fast was the object moving at the beginning of the timed interval?
According to your previous calculation, what was its average speed during this interval?
Do you think the object, when it reached the lower end of the book, was moving at a speed greater or less than the average speed you calculated?
your brief discussion/description/explanation:
initial speed=(d/t)*(a*t/2)=(.11)*(.1785)=.02m/s
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Your calculation of initial speed isn't correct. The units of the calculation d / t * a * t / 2 are not m/s, and that calculation won't give you initial velocity.
Presumably the ball started from rest so its initial velocity was 0.
OK, I think I see what you're trying to do with this step. d / t would be the average velocity. a * t would be the change in velocity, so a * t / 2 would be half the change in the velocity. Adding half the change in velocity to the average velocity would give you the final velocity; subtracting half the change in velocity from the average velocity would give you the initial velocity.
So using your notation
v0 = (d / t) - (a * t / 2)
and
vf = (d / t) + (a * t / 2).
We will be using different notation in this course, but it appears that you were close to the right idea.
However no acceleration has been determined for this motion, so any calculation based on a would not work in this situation.
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The objeects average speed was .11 m/s
Final Speed=at+v= .17*2.1+.02=.36m/s
Change in Speed=final speed-initial speed=.36-.02=.34m/s
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List the following in order, from least to greatest. Indicate 'ties': The object's initial speed, its final speed, its average speed, and the change in its speed as it rolled from one end of the book to the other.
your brief discussion/description/explanation:
Initial speed(.02m/s),average speed(.11 m/s),change in speed(.34m/s),final speed(.36m/s)
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Devise and conduct an experiment to determine whether or not the object is speeding up as it rolls down the incline. If you have set the experiment up as indicated, it should seem pretty obvious that the object is in fact speeding up. But figure out a way to use actual measurements to support your belief.
Explain how you designed and conducted your experiment, give your data and explain how your data support your conclusions.
your brief discussion/description/explanation:
To test whether speed increased I doubled the elevation of the book to test if the change in speeds would be double their previous values
Book Elevation:.016 m measured by ruler
Book Length: .24 m measured by ruler
Book Width:.02 m measured by ruler
Car Mass: 56.7 grams gathered from online sources
Travel Time: 1 seconds measured using timer
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Good to here. You don't have a valid force, so the acceleration you calculate is not correct.
However we haven't yet begun to use acceleration in this course.
What you know is that the car traveled .24 meters in 1 second, presumably starting from rest.
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Force: 9.8m/s
a=f/m= 9.8/56.7=.17m/s^2
Initial speed=.04 m/s
Average speed=.24 m/s
Final speed= .21 m/s
My data shows that given a higher angle of inclination the time it takes the car to reach the was a litle less than half of the previous values while the speeds reached were only doubled in the initial and average categories and the final speed was less
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Your instructor is trying to gauge the typical time spent by students on these experiments. Please answer the following question as accurately as you can, understanding that your answer will be used only for the stated purpose and has no bearing on your grades:
Approximately how long did it take you to complete this experiment?
48 minutes
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You may also include optional comments and/or questions.
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You have good data, but you have gone a little beyond the scope of what we have done so far in calculating force and acceleration.
You have determined average velocities, and you are showing excellent initiative.
Check my notes. We will be addressing the concepts of force and acceleration soon.
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