6. 6
Steady state: all the speeds are zero
3kx1 - 2kx2 = m1g
-2kx1 + 3kx2 - kx3 = m2g
- kx2 + kx3 = m3g
Spring-Mass Systems (cont.)
1
1
1
2
1 2
2
1
2
kx
g
m
x
x
k
m
dt
x
d
U
D
dt
x
d
F
F
m
2
2
Mass m1: FU = kx1; FD = 2k(x2 – x1) + m1g
2
3
3
3 2
3
2
x
x
k
g
m
m
dt
x
d
1
2
2
2
3
2 2
2
2
2
x
x
k
g
m
x
x
k
m dt
x
d
Mass m3:
g
m
g
m
g
m
x
x
x
k
k
k
k
k
k
k
3
2
1
3
2
1
0
3
2
0
2
3
Stiffness matrix
Mass m2