The Experimental Method: Answers

1) The slope of the incline was varied to see how it effected the time it took the ball to roll down the incline. So, SLOPE is the independent variable and TIME is the dependent variable.

2) Note that as the slope changes so does the height of the incline. The length of the incline also changes with slope. So incline HEIGHT and incline LENGTH could be confounding variables.

3)

Incline SLOPE TIME in seconds
1.00 3.0
0.50 4.5
0.33 5.0

4) see FIGURE.

5) As the incline decreased in slope from 1 to 0.33, the time it took the ball to roll down the incline increased from 3 to 5 seconds. Since the slope of the line is: -3, the equation relating time (DV) to slope (IV) is: Time = -3* Slope + 6. The slope is found by finding the distance over which the line rises (or in this case falls), which is -2 (3 sec - 5 sec), and dividing by the distance over which the line runs in the horizontal distance, which is 0.67 (1 - 0.33), so:

the slope of the line = m = -2/0.67 = -3. So, at this point for an incline of slope 1, the equation looks like:

3 sec = -3(1) +b, this must mean that b is 6 secs.

Checking the relationship yields:

3 sec = -3(1) +6; 4.5 sec = -3(0.50) + 6; and 5 sec = -3(0.33) +6.

Thus, the equation of: TIME = -3(SLOPE) + 6, fits the data completely and as such it can be used to describe the relationship between the independent (Slope) and dependent (Time) variables in this experiment.

6) A series of different experiments could be done in which the slope is kept constant as height is changed and incline length is changed. By comparing the results from these experiments, a decision can be made as to which variables control the time it takes the ball to roll down an incline. As a result, a firm functional relationship between the dependent and independent variable can be established so that the relationship is not confounded.