A force F cos (ω t) is applied to a spring of mass m = 1 kg and spring constant k = 100 N/m. If the applied force remains constant in magnitude, the displacement on the spring is maximum when the applied frequency (cycles per second) is about
1. 1.6 Hz
2. 16 Hz
3. 160 Hz
4. 0.16 Hz
5. 1600 Hz