This is a simulation for a particle(ball) move on top of a curved surface with z=a (x[sup]2[/sup]+y[sup]2[/sup]).
The red arrow is the velocity for the particle and black arrow is the normal force.
You can change the viewing angle with mouse (click and drag).

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Enjoy the fun of Physics! You can access this simulation online from
Ball move on top of a curved surface z=a(x^2+y^2)
Designed by Fu-Kwun Hwang (http://www.phy.ntnu.edu.tw/ntnujava/)
Deptartment of Physics, National Taiwan Normal University, Taiwan