# Why does a rolling disc topple less easily than a standing one?

If a force is applied perpendicular to the surface of a disc it topples sideways. Also, a stationary disc topples more easily than a rolling one. The explanations I've seen for this state that since the rolling disc has angular momentum it requires more torque to topple. But how can a force perpendicular to the surface of the disc produce torque?

• The magic word you seek might be "gyroscope"
– user854
Nov 22, 2014 at 20:16