What is the purpose of the following fixedpoint iteration xk

What is the purpose of the following fixed-point iteration? x_k+1 = 2x_k - x^2_k y

Solution

Given: Initial Velocity v_i = 12 m/s,
Final Velocity v_f = -12m/s,
mass m = 0.15kg,
Impulse J = ?
Impulse is given by
J = mv_f - mv_i
= m(v_f - v_i)
= 0.15 Kg (-12 -12) m/s
= -3.6N.