final velocity of train
m1 v1 = ( m1 + m2) v
2000* 3.5 = ( 2000 + 4500) v
v = 1.077 m/s
using energy conservation
0.5 m v^2 = 0.5 k x^2
6500* 1.077^2 = k * 2.1^2
k = 1700 N/m
IBH 000 110 x 10-10 m) What would be Suppose you want to make a black...