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course phy241
10/24 3
Lab activitiesNotes:
Include concise explanation: Whether specifically requested or not, all responses should include a brief explanation or description beginning on the line following other requested information. Abbreviations and incomplete grammar are acceptable; if you go too far with this I'll let you know, but I don't want to keep typing demands reasonable.
Reporting data:
Data consists of what you observed, not what you concluded or how you got from observations to conclusions.
Data should be presented in the specified format. If no format is specified, give a succinct data report in the form of a table.
Unless otherwise specified, data should consist of numbers, with a subsequent note on the meanings and units of the numbers.
Basic rule: Don't bury your data in a paragraph of explanation. It's OK if it appears that way within your explanation, as long as there's a succinct data summary.
Explaining your analysis:
Typically the explanation of your analysis will include some combination of symbolic and numerical results in a sample calculation of one result.
Other results should be reported in specified format; if no format is specified a list or a table would be appropriate.
1. Projecting point on CD onto paper on tabletop.
`qx001. Your points will lie along (or close to) an x axis perpendicular to the line you sketched on your paper. With the origin at the center point, what were the positions of your points corresponding to theta = 0, 30, 60, 90, 120, 150 and 180 degrees? Report as 7 numbers separated by commas in the first line, with brief explanation starting in the second line.
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6.2cm,4.8,3.3,0,-3.35,-4.35,-5.35
points all sat on a straight line and that is each points distance from the origin with theta=0 being positive and theta= 180 as the negative direction
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`qx002. What were the coordinates of your points corresponding to theta = 180, 210, 240, 270, 300, 330 and 360 degrees?
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(-5.5,0),(-4.5,0),(-3.5,0),(0,0),(3.5,0),(5,0),(6,0)
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`qx003. Suppose the disk rotated with a constant angular velocity, with an actual object moving along the tabletop just below the point on the disk. How would the velocity of that object change as the disk rotated through one complete revolution? Sketch (on your paper) and describe (below) a graph representing the velocity vs. clock time behavior of that point. Include an explanation connecting your results to your data.
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All i can figure is there is a relation between distance travelled on the table and the arc length of the circle. But the circle could rotate evenly with a pendulum if the pendulum only went as far as the edges of the cd.
The question is, when would the object be speeding up, when would it be slowing down, etc../h3>
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`qx004. For the same object as above, sketch a graph representing the acceleration vs. clock time behavior of that point. Desribe your graph and include an explanation connecting your results to your data.
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`qx005. For the same object, sketch a graph representing the net force on the object vs. clock time for one revolution of the disk. Describe your graph and include an explanation connecting your description to your data.
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... describe r, v and a vectors ...
2. Quick collision experiment
`qx006. In the first line below give the landing positions of the 'straight drop', uninterrupted steel ball, the marble, and the steel ball after it collides with the marble, separated by commas.
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2.5cm,21.5cm,21.5cm,11cm
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In the second line, report the horizontal displacement of the uninterrupted steel ball, the marble, and the steel ball after it collides with the marble, separated by commas.
Starting in the third line give the units of your measurements and a brief explanation.
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64cm,19cm,53.5cm
Its just `dx, all but the marble went down the ramps first, subracted 2.5 because the straight drop was 2.5 cm so the paper started that far before the end of the last ramp
The distance down the ramp isn't relevant to the analysis of the falling ball. The free fall doesn't start until the ball loses contact with the ramp.
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`qx007. Assuming that the time of fall was .4 seconds, what do you conclude was the velocity of each object at the instant it left the end of the last ramp? Report three numbers separated by commas in the first line, in the same order used in the preceding question. Units, explanation, etc. should start in the second line.
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160,47.5,133.75
cm/s,just divided the distance traveled by the time it to took to hit that point
you would only divide the distance traveled in the fall by the time of fall
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`qx008. In the collision, the velocity of the steel ball changed, as did the velocity of the marble. What was the change in the velocity of each? Report number in the first line, brief explanation in the second.
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steel ball:-26.25cm/s,marble:47.5cm/s
Just subtracted the difference of velocities in the steel ball, the marble started from rest
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3. Motion of unbalanced vertical strap
`qx009. The original vertical strap system oscillated about an equilibrium position with one end lower than the other. Why do you think the equilibrium position had that end lower?
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cause it wasnt 100% completely balanced
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`qx010. What changed about the behavior of the system when a couple of #8 nuts were added to the higher end? What is your explanation?
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It spun, it was above the center of mass
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`qx011. Would it have been possible to balance the system at a position where the end with the #8 nuts was higher? Would it have been challenging to do so? Explain.
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Yes, it wouldnt be easy, you would have to change the center of mass
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`qx012. Did the frequency of oscillation of the system appear to be constant?
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yes,until it got too slow to turn over
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4. Balancing the styrofoam rectangle
`qx013. Was the styrofoam rectangle easiest to balance when the paperclip was inserted along an axis through the point below its center of mass, at a point above its center of mass, or at the point of its center of mass? Why do you think it was so?
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below,because its not trying to ""fall""
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`qx014. At which positions of the paperclip did the system did the system oscillate? At which positions did it appear to oscillate with constant frequency? At which positions did it appear to oscillate with nonconstant frequency?
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When it was above the center of mass.?
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5. Two cars with repelling magnets
`qx015. Why do you think the two cars traveled different distances when released?
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Because they are different masses
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`qx016. Which car do you think exerted the greater force on the other?
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6. Graphs
`qx017. The graphs you were given in class depict coasting distance, in centimeters, vs. separation in centimeters, for a 120-gram toy car whose acceleration due to friction is 15 cm/s^2 (plus or minus an uncertainty of 10%). Sketch four tangent lines to the first curve, spaced equally from near one end of the curve and the other. Find, with reasonable accuracy, the coordinates of two points on each tangent line, and use these coordinates to find the approximate slope of each tangent line. In the first line below, report your four slopes. In the second line report the x and y coordinates of the two points used to find the slope of the third tangent line, reporting x and y coordinates of the first point then x and y coordinates of the second, using four numbers separated by commas.
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-20,-15,-9.4,-5.4
(4,40)(2,80),(5.5,20)(2.5,65),(8,4)(1.5,65),(9.3,10)(2.4,47)
(3.5,50),(4,43),(4.3,40),(5.5,28)
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`qx018. Each centimeter of coasting distance corresponds to very roughly 2000 g cm^2 / s^2 of energy lost to friction. That energy came from the potential energy of the magnets at the given separation. So the vertical axis of your graph can be relabeled to represent the energy lost to friction, and hence the potential energy of the magnet system. For example, 20 cm on the vertical axis corresponds to 20 cm of coasting distance, each cm corresponds to 2000 g cm^2 / s^2 of potential energy, so the 20 cm coasting distance corresponds to 20 * 2000 g cm^2 / s^2 = 40 000 g cm^2 / s^2 of potential energy. The number 20 on the vertical axis can therefore be cross-labeled as 40 000 or 40 k, representing 40 000 g cm^2 / s^2 of PE. You should be able to quickly relabel the vertical axis of your graph.
Using the relabeled vertical coordinates, find the y coordinates of the two points you used to find the slope of your third tangent line, then report the x and y coordinates of those two points as four numbers in the first line below. In the second line report the rise and run between these points, and the slope. In the third line report the units of the rise, the units of the run and the resulting units of the slope. Starting in the fourth line explain what you think the rise means, what the run means, and what you think the slope means.
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(4,80k)(2,160k),(5.5,40k)(2.5,130k),(8,9k)(1.5,130k),(9.3,20k)(2.4,97k)
-40,-30,-18.6,-11.2
rise is k run is in cm slope is k*cm^2/s^2
Right idea, but the k represents 1000. The units of the vertical coordinate are g cm^2 / s^2; in this case since you reported in units of 1000 (that's your k) the units would be kg * cm ^2 / s^2.
The rise is the energy lost to friction,run is the separation between the two magnets,slope tells the force
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`qx019. Report the slopes of all four of your tangent lines, in terms of your relabeled coordinates, as four numbers in the first line below. You can easily and quickly find these four slopes from the slopes you previously reported for the four tangent lines. Starting in the second line report very briefly how you found your slopes.
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-40,-30,-18.6,-11.2
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`qx020. University Physics Students: Find the derivative of the given y vs. x function y = 88 x^1.083 (this is a simple power function with a simple rule for its derivative) and evaluate at each of the four tangent points. Give the derivative function in the first line, in the second line the values you got at the four points, and in the third line compare your values to the slopes you obtained previously.
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y'=95.304x^.083
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`qx021. University Physics Students: What is the specific function that describes PE vs. separation for the magnet system? What is the meaning of the derivative of this function?
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not bad, but see my notes and let me know if you have questions
I'm not going to require it but if you want to submit a revision, read on to the next instruction
&#Please see my notes and submit a copy of this document with revisions and/or questions, and mark your insertions with &&&& (please mark each insertion at the beginning and at the end).
Be sure to include the entire document, including my notes. &#