An undamped vibrating system consists of a spring whose scale is 35 kN/m and a mass of 1.2 kg. A step force F = 50 N is exerted on the mass for 0.040 s.

(a) Write the equations of motion of the system for the era in which the force acts and for the era that follows.

(b) What are the amplitudes in each era?

(c) Sketch a time plot of the displacement.