Proficiency 3

Problem: What effect does the degree of slope have on the acceleration of a marble?

Hypothesis: I believe the steeper the slope, the faster the acceleration because the higher the angle, the more gravity has an effect on the ball.

Experiment:

Variables-
IV- degree of slope
CV- same ball, same inclined plane, same person timing
DV- time of trial
Control- straight drop

Materials-
12 inch inclined plane
Stopwatch
Ruler
Marble

Procedure-

1. Gather all materials
2. Construct the inclined plane so it's at a 25 degree measured to the top of the plane and has a mark on it six inches down from the top
3. Mark another line at another six inches down from the previous mark
4. Roll the marble down the plane
5. Start the stopwatch as the marble begins to roll
6. Wait for the ball to reach the six inch mark
7. Stop the watch as the marble rolls over the mark
8. Start the second stopwatch at the six inch mark
9. Stop the stopwatch when the marble crosses the mark twelve inches from the top
10. Record results
11. Repeat steps 4 through 9 with the 25 degree slope twice more
12. Change the plane to a 45 degree slope
13. Repeat steps 4 through 9 three times with this arrangement

External Variables:
In a conscious way, I attempted to eliminate external variables to make the test more accurate. To begin with, I built sides on the inclined plane to insure that the ball would roll straight down and not off the side. Next, I measured the angle of the plane twice before each test, once to set it up and again after the marble was being held on there, because any small shift could have an effect on the outcome of the experiment. Finally, I marked the spot to stop the stopwatch as clearly as I could to help me to stop the watch as quickly as I could. Even so, I'm not perfect so it wasn't completely accurate, but because of my elimination of external variables, I think it is closer than it would have been without them.

Observations:

                                    Trial 1           Trial 2           Trial 3          Average
25 degree slope             60.80            27.46            29.83         39.36
45 degree slope             19.78            45.45            60.22         41.82
***All numbers represented in in/s/s***



 Conclusion:
I recently experimented with speed and acceleration to see if there is a difference between the acceleration of a marble when rolling down different slopes. Because of past experience of going down steep hills in a car, I believed that a with a higher slope, the marble would accelerate more and have a faster time rolling down the inclined plane. With the tests that I completed, I found that my hypothesis was supported by the facts. When the marble was rolling down the 25 degree slope, it had an average rate of acceleration of 39.36, while the 45 degree slope allowed the marble to have an average rate of acceleration of 41.82  in/s/s. This is figured out by subtracting the initial velocity from the final velocity and dividing this by the total time. Though the final and initial velocities were very similair in both tests, the total time was shorter for the 45 degree slope, which means the marble accelerated more on it. Since there is less support underneath it, the marble is in more a freefall which means it accelerates more. Also, the mechanical advantage of an incllined plane is calculated by dividing the length of it by its height. Because the length of the plane stayed the same but the height changed, the 45 degree slope had less of a mechanical advantage than the 25 degree slope. The more machanical advantage there is, the less energy transfer and the less acceleration.

Speed and acceleration have a simple relationship. The more acceleration, the more speed. An example of this is a race. If two cars start out at 20 mph and one accelerates at a higher rate than the other, its final speed will be greater than the other.