What phenomenon occurs when a spinning object is acted on by an external force?

• A. Precession
• B. Attenuation
• C. Diffraction
• D. Refraction

Answer: (A)

When a spinning object experiences an external force, the torque from that force changes the direction of its angular momentum rather than its spin speed alone. If the torque is perpendicular to the spin, the angular momentum vector slowly sweeps around the torque axis, causing the whole spinning object to exhibit a gradual rotation of its axis called precession. This is the familiar behavior seen in gyroscopes and spinning tops: gravity provides a torque that makes the axis precess while the spin remains fast.

A helpful way to think about it is that the rate of precession depends on how hard the torque pushes on the spinning body and how fast it is spinning: stronger torque and slower spin produce faster precession, with the relation roughly Ω_p ≈ τ / L.

Attenuation describes a loss of amplitude or energy, which isn’t about changing the orientation of the spin axis. Diffraction and refraction involve wave behavior—bending and changing direction as waves encounter obstacles or move between media—not the rotational dynamics of a spinning object under torque.