Lab 2 - Acceleration of Gravity

Objective:  To determine the acceleration of gravity for a free falling object, and to continue to gain experience with the data collecting hardware and computer programs.

Procedure:  Once the hardware is set up and tested, toss a ball into the air and track the position versus time and velocity versus time using the graphing software.  Track this for at least 5 repetitions and average out the data.

Data:  Below are the 5 data captures that were used for this experiment.  Curve fit and line fit were used to determine the best tests to use



Ball Toss Test 1

Ball Toss Test 2

Ball Toss Test 3

Ball Toss Test 4

Ball Toss Test 5

Possible sources of Error:
1. The easy answer to this is that we had different students tossing the ball in different ways.  One student would throw the ball higher than another, there was hesitation and the way the ball was held seem to make a difference as well.

2.  Since the tracking sensor is just that, and sensor, it would sense other movement with the movement of the ball.  For example, several of the test that were not used were due to the movement of the ball thrower, people walking by and other movements that occurred during the testing.

3.  Our own interpretation as a group.  What I mean by this is that if one of us thought that it was a good result, someone else may have wanted to throw it out.  This may have caused us to settle for a less accurate test, or may have given us an improvement.  Hard to say really.

Questions:
1. Why should it be a parabola?  The position versus time graph should be parabolic because gravity = 9.81 m/s^2.  Acceleration is constantly slowing down on the way up, and constantly speeding up on the way down at the same rate.  In relation to this experiment, gravity slowed down the ball on the way up, and sped it up on the way down.  When interpreting to velocity versus time, the line is linear.

2. Why does the slope have a negative slope, and what does the slope of this graph represent? The graph represents gravity, and since gravity is -9.81 the linear graph will slope in the negative direction.

3.  Results from falling body experiment.

Percent error = (measured - actual)/actual * 100

Actual = 9.81

Average from the 5 Tosses

Conclusion: The experiment produced results that were close to what was expected.  The percent error could have been better with a little more time. and more tests.  The results were pretty close to the given force of gravity that was used in the percent error calculation.

In the end, we were able to determine a close proximity to the force of gravity with the experiment that was performed.  Given additional time and practice, I feel confident that we could have come very close to 9.81.