# TP1 10.29 Two Masses fixed to walls
# Two equal masses m are connected to each other by a spring (spring constant D) and on either side to a fixed wall.

# m*s1'' + 2D*s1 - D*s2 = 0 => s1'' = -D/m*s1 -D/m*s1 + D/m*s2
# m*s2'' + 2D*s1 - D*s1 = 0 => s2'' = -D/m*s2 -D/m*s2 + D/m*s1

coefficient(1): D/m_1 # D/m for s1
coefficient(2): D/m_2 # D/m for s2, identical to D/m_1
coefficient(3): -1 -> -s1_0 # initial position of s1
coefficient(4): -1 -> -s2_0 # initial position of s2

iintegrate -D/m*s1, -D/m*s1, D/m*s2 -> -s1' # input is s1''
iintegrate -s1' -> s1
   IC: -s1_0
s1 * D/m_1 -> D/m*s1
invert D/m*s1 -> -D/m*s1

iintegrate -D/m*s2, -D/m*s2, D/m*s1 -> -s2' # input is s2''
iintegrate -s2' -> s2
   IC: -s2_0
s2 * D/m_2 -> D/m*s2
invert D/m*s2 -> -D/m*s2

output(x): s1
output(y): s2