Nicole+and+Erica


 * Lab: ** Bombs Away


 * Group Members: ** Nicole Margulis and Erica Levine
 * Class: ** Period 2
 * Date Completed: ** 9/27/10
 * Date Due: ** 9/28/10


 * Objective: ** To find what is the acceleration due to gravity.
 * Materials: ** spark tape, spark timer, clamp, tape measure, mass


 * Hypothesis: If we drop a weight at free fall through the ticker-timer, the dots on the tape should be increasingly far apart due to the increasing velocity of the weight. If we graph this data, we can find the velocity and any point during the fall, and therefore the acceleration. We expect to get a number near 981 cm/s2 because this is the known value of acceleration due to gravity. **

1) Clamp the spark timer set to 60 hertz to the top of the cabinet 2) Feed a piece of spark tape about 1.5 meters through the timer 3) Use tape to attach the weight to the spark tape 4) Turn on the timer while simultaneously letting go of the weight 5) Tape the spark tape to the table 6) Measure the distance of each dot from the start 7) Record data 8) Use the data to make a distance-time graph 9) Perform calculations to determine the acceleration due to gravity
 * Procedure: **

[|Nicole Erica acceleration of gravity.xls]
 * Data: **


 * Calculations: **

To find acceleration: y= Ax 2 + Bx d= A(t) 2 + B(t) d= Bt + 1/2at 2 d= Vit +1/2at 2

A=1/2a 446.4= 1/2a
 * 892.8 cm/s2 = a**

To find percent error:

Error= |(experimental value- theoretical value|/ theoretical value) x100 Error= |892.8- 981|/981 x100
 * Error= 9.00%**


 * Discussion Questions: **

1) Does the shape of your graph agree with the expected graph? Why or why not? Yes, the shape of our graph agrees with the graph we expected. Our object started with a velocity of zero and as time went on, it accelerated to gravity’s velocity and the distance away from the timer increased. With this information, we expected our graph to have an increase in distance and velocity shown by a polynomial graph as time increased. We know it is accurate because our r2 value was 0.9999 degrees.

2)How do your results compare to that of the class? (Use Percent difference to discuss quantitatively) The class average of the experimental value of g was 848.65 cm/s2. Our value was 892.8 cm/s2. To find the percent difference, we can calculate the absolute value of the difference between the two values (|848.65-892.8|) and then divide that by the class average (848.65). Then multiple that value by 100. The percent difference then equals 5.20%.

3) Did the object accelerate uniformly? How do you know? The mass in this lab was accelerating due to gravity. When objects are free-falling, gravity is a constant force on it. As a result, the mass was accelerating uniformly as it fell.

4. What should the velocity-time graph of this object look like? - The velocity time graph of this object in free-fall would start at the origin. It would be a straight slanted line with a positive slope. This is because as time progresses, the acceleration increases due to the force of gravity.

5. Write down the expected equation of the line from this v-t graph (use specific information from you x-t graph). y= 892.76x

6. What factor(s) would cause acceleration due to gravity to be higher than it should be? Lower than it should be? - Acceleration due to gravity could end up higher than the accepted value if a force caused the tape to move through the ticker-timer faster than normal. An example of this would be a person's hand accidentally pulling the paper through the ticker-timer. - Acceleration due to gravity could end up lower than the accepted value if there was an interference with the free flowing tape. An example of this would be running the tape through your fingers, or having it drag over the top of the cabinet. Also, the setup of the graph, in which the paper flowed through the ticker-timer (not exactly freely) could slow down the motion and yield a lower acceleration than expected.

**Conclusion:**

The purpose of this lab was to find the acceleration due to gravity using our given materials, which my partner and I did successfully. Our hypothesis stated that the dots on the ticker-timer would be increasingly distant from each other, which was the result because of the increasing velocity during the fall. We made a chart of our results and turned it into a graph, which generated the equation y=446.38x 2 -33.094x. Since the x values represent time on the graph, we were able to replace the xs in the value with the time of the fall.By manipulating previously known equations we were able to recognize that the A value represents 1/2 of the acceleration of the free falling weight. Our A value was 446.4, which made our acceleration 892.8 cm/s2. This result reflects our hypothesis because the it is fairly close to the known value of acceleration due to gravity, 981. The percent error of our results was 9.00%. Our experimental value came out below the theoretical value for acceleration due to gravity. This error most likely occurred for two reasons. The first reason is the set up of the experiment. Because the tap ran through the ticker-time it wasn't really in free fall, which would cause our experimental acceleration to be low. The second reason is the way we conducted the experiment. When the tape was running through the ticker-timer, it was also running through my fingers as i tried to guide the fall. This absolutely affected our result, in that it slowed the speed of the free falling weight, therefore also lowering the acceleration. In the future, to get more accurate results it is important not to let the tape run through your fingers before it goes through the ticker-timer. Another error that we had was with our B value. Since the B value represents the initial velocity, the theoretical value of this variable is 0. Our B value was way off, at -33.1. A possible cause of this drastic error occurred in the beginning of the experiment. At the start, we didn't drop the weight right away and we even may have pulled it up in order to hold it.