Free Fall Lab
Group Members: Deanna Magda and Jae Li
Due: 9/30/10

Objective: What is the acceleration of a falling body?

Hypothesis: Over time, the velocity should increase due to acceleration due to gravity. true but didn't address the objective
Materials: Ticker Tape Timer, Timer tape, Masking tape, Mass, clamp, meterstick.

1. Set the spark timer to 60 hertz and attach it to the top of the inside of the cabinet door.
2. Obtain a piece of ticker tape about the length of the cabinet door and thread it through the spark timer, with the excess tape hanging over the top of the door. Use tape to attach a mass to the end of the ticker tape.
3. Turn on the spark timer and drop the mass.
4. Tape your ticker tape data to a table and measure the distance from dot zero to dot 1 using a meter stick. Continue to measure the distance between dot zero and the next dot. Record your data in an excel spreadsheet.
5. Use your data to construct a graph, including the trend line and the r2 value.

NOTE: Even though when preforming the experiment the object was moving downwards and that is normally negative, we decided that downwards was positive. Technically this still means that away is positive. This is why none of the acceleration values, distances, or velocities are negative and they are all positive.




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 expected graph. We expected the graph to start with a shallow slope and then gradually get steeper and we expected it to be positive. This is exactly what our graph did.

2. How do your results compare to that of the class? (Use Percent difference to discuss quantitatively.)
Our results were very close to the class results. Our precent difference was only .59% which means we were not very far off from the acceleration value of the class average. This is good because it shows that our results are consistent with multiple trials. In our class we had 9 different trials, including ours, with only one outlier, and the fact that we were only .59% different then the class as a whole it shows that our results are sound and pretty precise.


3. Did the object accelerate uniformly? How do you know?
Our object did accelerate uniformly because it is only one line. If the object had decelerated or even gone at constant speed the graph would have had a strait line or a negative sloped section. what does Uniformly mean?

4. What should the velocity-time graph of this object look like?
The velocity time graph would be a positive strait spelling? line. Because the acceleration is constant, the line will be a slanted line with a constant slope moving further away from its starting point over time. Because the initial velocity was 0 then the line should start at the origin or (0,0).

5. Write down the expected equation of the line from this v-t graph (use specific information from your x-t graph).
Being that the equation of our p-t graph is y=439.78x^2-13.588x, our v-t equation should come from that. It should also equal the acceleration because the slope of a v-t graph is acceleration. With this in mind we decided our equation should be y=879.56x. We set the y intercept to 0 because the initial velocity is 0.

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 would be lower on objects with a high surface area because of wind resistance. However because our object did not have a high surface area, air resistance is not a factor. The major factor that would make the acceleration lower then it should be would be friction. The ticker tape is rubbing up against something before it goes through the spark timer and that friction causes the tape to go through just a little slower. It would be higher is air was pushing down on the object.

In this lab we learned about acceleration due to gravity. Gravity is all around us and we literally experience it every day. However, before this lab we could not have understood the physics behind it. As we hypothesized, the mass increased as it fell. Our experimental data was close to the actual value. specific values?
Outside the physics classroom, there are many examples of acceleration due to gravity. If you were to go skydiving, you would be experiencing acceleration due to gravity first hand. You see it every time you drop a pen. It would be even clearer if you were to accidentally drop a penny off a tall building or drop something out a window. Each of these things accelerates as they fall, and because of this lab, we now know the actual acceleration at which that happens.

Sources of Error: no headings here. should flow smoothly
In this lab, the largest source of error was friction. The tape has to come in contact with the spark timer, and was also draped over the top of the door. The contact between the tape and the objects around it caused friction, which slightly counteracted the gravity. This is why our data was slightly lower than the actual value.
Also, we were only measuring to the 100th of a centimeter, with the last digit being uncertain. Although this did not greatly affect our data, it is still important to note that our measurements, although precise, were not completely accurate.

Next time we do a experiment again, if we do, then we know that there are certain things we could do to make our data more precise and accurate. We could try to reduce the amount of friction in the experiment. By making sure that the ticker tape comes in contact with as little as possible then we know that the friction is reduced as much as humanly possible. how exactly?