def f(t, p):
    """
    defines the disturbance force input to the system
    """
    m, k, c, Distance, StartTime, Amax, Vmax, DistStart, F_amp = p
    
    # Select one of the two inputs below
    # Be sure to comment out the one you're not using
    
    # Input Option 1: 
    #    Just a step in force beginning at t=DistStart
    # f = F_amp * (t >= DistStart)
    
    # Input Option 2:
    #    A pulse in force beginning at t=DistStart and ending at t=(DistStart+0.1)
    f = F_amp * (t >= DistStart) * (t <= DistStart + 0.1)
    
    return f