up

top margin: 50

up

top margin: 25

up

top margin: 0

up

Now that you are using more frames,
in order to keep the ball bouncing at the same rate
(one bounce per second)
you  need to increase the frame rate.
The frame rate is the rate of frames per second (fps).
In this case, you are increasing the frame rate
from 2 frames per second to 4 fps.
Even though you are using five total frames,
the first frame gets re-used for the downward and upward
motion of the ball,
so you only need to count it once
for the purpose of determining the frame rate.