Figure 2. The segmented and ‘cleaned’ images of the ball in free fall motion.

Since the position of the ball is not exact, estimation is done to determine the position of the ball. Estimation is done by getting the positions of the white pixels. The x positions as well as the y positions were averaged. Table 1 shows the average values of the ball position (x and y). The distance was determined using the distance formula:

h = [sqrt (x2 - x1)^2 + (y2 - y1)^2]

The resulting h here is the distance from the average position of the ball to another position at a different time in pixels. Since we do not want to express gravity in pixels per second squared, we convert the pixel values in meters. It is found the 966 pixels are in 1 m. Using this conversion factor, the value of the actual distance in meters is obtained. Lastly, the value of the gravity is obtained using equation 1. Time t is obtained by dividing the number of frames that have passed, with the frame rate which is 20 frames per second. Table 1 summarizes the results obtained.

Table 1. Calculation of g. The average position of the ball, the height travelled in pixels and meters and the value of the gravity calculated.