Answer: π/2.
- A π/2
- B 0
- C π
- D π/4
Correct answer: A. π/2
Explanation: At resonance, the displacement lags the driving force by exactly π/2 (90°). Below resonance the lag is less; above resonance it approaches π.
In SHM, displacement and velocity are 90° out of phase (v is maximum when x=0, and zero when x is extreme), while acceleration is always exactly opposite in sign to displacement, consistent with a = −ω²x.
Concept context
Simple harmonic motion, spring-mass, pendulum, energy in SHM, and resonance.