[Visualpython-users] bounce.py and coefficient of restitution

[Frank N. <fra...@sb...>]

Hello everyone,

My students are enjoying using VPython and are learning quickly.  My first
assignment is to have students modify the bounce.py program in a variety of
ways.

I'd like for them to add a coefficient of restitution to more closely simulate
the bouncing of a real ball.  My thinking is to modify the ball/floor impact
detection statement to read:

if (ball.pos.y <= ball.radius):
        ball.velocity.y = -c*ball.velocity.y

where "c" is the coefficient of restitution.

Using a drop height of 20, an initial velocity of 0, and c = 0.85, the ball
only bounces once and then sticks to the floor :(

Changing only the drop height to 10, the ball now bounces 7 times before
sticking to the floor. :|

Shouldn't the ball bounce forever (just to a smaller height on each successive
bounce)?  And why does changing the drop height matter?  What's going on?

Thanks,
Frank Noschese
John Jay High School
Cross River, NY