Gyroscopic Effect
In figure (a), a person holding the spinning bike wheel lifts it with her right hand and pushes down with her left hand in an attempt to rotate the wheel. This action creates a torque directly toward her. This torque causes a change in angular momentum ΔL in exactly the same direction. Figure (b) shows a vector diagram depicting how ΔL and L add, producing a new angular momentum pointing more toward the person. The wheel moves toward the person, perpendicular to the forces she exerts on it.
Source
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"OpenStax College, College Physics. November 17, 2012."
http://cnx.org/content/m42184/latest/?collection=col11406/1.7
OpenStax CNX
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