# Rolling ball, change of direction

• I
• jonbarril
In summary, when exerting lateral forces on a free-rolling ball on a plane with no slipping, the resulting path of the ball will depend on the interaction between friction and gyroscopic effects. If a force is applied from the South, the ball will start rolling to the North and eventually reach a constant speed. If the same force is suddenly applied from the West, the ball's path will change and it may end up rolling in a North-East direction. The apparent axis of rotation may also change from horizontal to eventually North-South, but this is conjecture and further input is needed.
jonbarril
Say I have a magic way to exert lateral forces on a free-rolling ball on a plane, with no slipping. Say I apply a force for a given period from the South, the ball starts rolling to the North and attains a constant speed. Then I suddenly apply the same force for the same period but from the West. What is the resulting path of the ball on the plane? What is the path of the balls apparent axis of rotation (how does it change from East-West to eventually North-South, does it remain horizontal)?

Thanks
--jon

If you apply just a force at the ball's CoM, and it starts rolling, the you must have friction. If you then apply the lateral force you will have an interaction of friction gyroscopic effects, which can get quite complex and counter intuitive:

Last edited:
scottdave and PeroK
Forces are associated to accelerations.
How do you believe the trajectory will change?

It has been a long while since I took physics. I think the gyroscopic effect will work in favor of helping to turn the ball to the East. My guess is that the ball would end up rolling North-East. Not sure if the axis of rotation would stay flat. This is all complete conjecture. I'm hoping folks out there can give a more informed description of the ball's motion.

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