Results
An example of position and time data obtained
from the video is shown in figure 2.
The Sensor Tools app collects video data in pixels and then,
based on the height of the person standing on the skateboard,
converts the units into metres. The camera frame frequency of 30 frames per second
(fps) delivers constant time intervals between subsequent video frames.
The app also produces velocity–time graphs for each coordinate separately (figure 3).
First, we determine the velocity of both objects in the x-direction and find a nearly constant value of vS ≈ 2.2 m s−1, as expected. Differentiation of equation (2) yields
vy,B(t) = −gt + v0.
From figure 3(c) we find g = −9.78 m s−2 and v0 = 5.5 m s−1.
The value of g deviates by no more than 0.3% from the theoretically expected
value of gtheo = 9.81 m s−2.