# Does precession of a rigid body change instantaneously?

I read some explanations of precession; this side for example summarizes briefly almost all what I have understood so far.

But one thing bothers me: Following all this formulas, the precession velocity is constant as long as the external torque is applied constantly. So let there be a spinning disk without external torque (so no precession, the rotations axis keeps its direction). If I now start to apply some constant torque to change the rotation axis, does the precession velocity jump instantaneously to the calculated, constant value? Is there no "precession acceleration phase" or something?

• Hi I could be wrong, but I don't think any classical effect could occur instantaneously...anybody got any example to say they do? regards – user74893 Mar 18 '15 at 13:16
• Thats exactly what i am thinking, but I cannot find anything describing the acceleration of the rotation axis' movement. – Horstling Mar 18 '15 at 14:12
• How do you start to apply a constant torque without a torque ramp-up phase? – ja72 Mar 18 '15 at 15:20