initial timing experiment

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.

** template form

Initial Timing Experiment

You may enter any message or comment you wish in the box below:

________________ **

** ________

In this experiment you will use the TIMER program, a hardcover book, 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 on the Assignments page).

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.

Then reverse the direction of the book on the tabletop, rotating the book and its prop 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 solid glass marble, a small can of tomato paste (full or empty?), a ball-point pen), 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?

Note:  Don't trust this form.  Compose your answer in Notepad or a word processor, saving it every few minutes, then copy and paste it into the box.  Power could surge, your computer could malfunction, in any of a number of ways the work you put into this form could be lost.  Compose it elsewhere and keep a copy.

________________ **

 For this experiment I used the Giancoli Physics Sixth edition as the ramp it measured

28.4 cm long. The item that I am rolling is the small glass sphere that came with the lab kit it

measured 1.3 cm. To prop up the ramp I used a one subject notebook that was measured to be 0.7

cm thick and lined the ramp up with the edge of a design on the notebook to keep it the same

when I turned it around.

I rolled the ball along the crease between the binding of the book and where the front of

the book opens up. So that the marble will roll in a straight line.

Using the timer program I timed the how long it took for the marble to roll off the edge of the

book.

It took several tries to find something that would allow the marble to roll for at least 2

seconds on the first set up.

Initially I tried using the VHCC Catalog 2002008 as the prop for the book, but the marble

rolled too quick and it didn’t take at least 2 seconds to reach the end.

Then I tried using a small notepad, but the marble didn’t roll smoothly and it wanted to

stop as it rolled down the book.

** ________

In the box 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 see any patterns that might occur.

________________ **

The marble rolled 28.4 cm. Down a 1.3 cm incline.

Roll # Time in Seconds Roll # with Time in

On Initial 180 deg. Rotation Seconds

Setup

1 2.625 1 1.84375

2 2.54687 2 1.75

3 2.625 3 1.84375

4 2.546875 4 1.796875

5 2.609375 5 1.90625

6 2.53125 6 1.859375

Average of

6 rolls 2.5807 sec. 1.83333 sec.

** ________

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.

________________ **



Speed = distance / time

We will use the average speed to limit the effect of anyone reading being off.

Speed = 28.4 cm/ 2.5807 seconds on the initial setup and 28.4 cm / 1.833 seconds on the reversal

setup.

So the initial setup speed would be 11.0 cm/sec.

On the reversal roll the speed was 15.5 cm/sec.

If we take the difference between the highest roll and the lowest roll we have a measurement of

(2.625 - 2.54687) 0.7813 then we can divide that by the average of the rolls to get a measurement

of 3 percent difference in the measurements on the initial setup.

We can all so see between the 2 different setups that there is a difference of 0.7474 seconds this

is probably due to the setup location not being completely level to begin with.

To get a more accurate reading then we could use an area that has been calibrated to be

perfectly level.

It would also be of help to use sensors to start timing when the marble left the initial

location, crossed a center point, and then crossed the point where it rolled off the book. Then I

believe that we would be able to see that the marble is accelerating as it moves down the incline.

** ________

Devise and concuct 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.

________________ **



To determine if the marble is speeding up, we can find the center point and try to find the speed

of the marble when it crosses the center point.

Roll # Time in Sec.

1 1.703125

2 1.625

3 1.640625

4 1.71875

5 1.5708125

6 1.515625

Average 1.627322917 sec

The distance is now 14.2 cm and the average time it took to cross the center point is 1.627

seconds. So the speed at the center point is 14.2 cm/1.627 sec= 8.73 cm/sec

Comparing this speed to the initial setup speed of 11.0 cm/sec. We used this because I used the

same setup as the initial setup because the speed was slower and it would be easier to find the

speed at the half way point.

By comparing the speed at the center point (8.73 cm/sec) and the speed of the marble from the

initial setup (11.0 cm/sec) we can see that the marble is speeding up as it moves down the

incline.

** ________

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: 

________________ **

It took me almost 3 hours to complete this experiment.

** ________


You may add optional comments and/or questions in the box below.

________________ **

Very well done. This experiment wasn't intended to take that long, but the irregularities in the marble and the 2-second requirement appear to have pushed the limits of what is possible.